Recommit <chrono> changes with a couple xtra tests marked to fail on apple's clang. Reviewed as D51762

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@344627 91177308-0d34-0410-b5e6-96231b3b80d8

180 files changed, 10901 insertions, 2 deletions

diff --git a/include/__config b/include/__config
index 14ecb8fb4..7e47f4479 100644
--- a/include/__config
+++ b/include/__config
@@ -492,6 +492,11 @@ namespace std {
 
 #define _LIBCPP_ALWAYS_INLINE __attribute__ ((__always_inline__))
 
+// No apple compilers support ""d and ""y at this time.
+#if _LIBCPP_CLANG_VER < 800 || defined(__apple_build_version__)
+#define	_LIBCPP_HAS_NO_CXX20_CHRONO_LITERALS
+#endif
+
 #elif defined(_LIBCPP_COMPILER_GCC)
 
 #define _ALIGNAS(x) __attribute__((__aligned__(x)))
diff --git a/include/chrono b/include/chrono
index 069110101..75258abd2 100644
--- a/include/chrono
+++ b/include/chrono
@@ -748,6 +748,7 @@ unspecified
     parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp,
           basic_string<charT, traits, Alloc>& abbrev, minutes& offset);
 
+// calendrical constants
 inline constexpr last_spec                              last{};       // C++20
 inline constexpr chrono::weekday                        Sunday{0};    // C++20
 inline constexpr chrono::weekday                        Monday{1};    // C++20
@@ -1091,7 +1092,12 @@ typedef duration<long long,        milli> milliseconds;
 typedef duration<long long              > seconds;
 typedef duration<     long, ratio<  60> > minutes;
 typedef duration<     long, ratio<3600> > hours;
-
+#if _LIBCPP_STD_VER > 17
+typedef duration<     int, ratio_multiply<ratio<24>, hours::period>>         days;
+typedef duration<     int, ratio_multiply<ratio<7>,   days::period>>         weeks;
+typedef duration<     int, ratio_multiply<ratio<146097, 400>, days::period>> years;
+typedef duration<     int, ratio_divide<years::period, ratio<12>>>           months;
+#endif
 // Duration ==
 
 template <class _LhsDuration, class _RhsDuration>
@@ -1574,6 +1580,1020 @@ typedef steady_clock high_resolution_clock;
 typedef system_clock high_resolution_clock;
 #endif
 
+#if _LIBCPP_STD_VER > 17
+
+struct _LIBCPP_TYPE_VIS last_spec { explicit last_spec() = default; };
+
+
+class _LIBCPP_TYPE_VIS day {
+private:
+    unsigned char __d;
+public:
+    day() = default;
+    explicit inline constexpr day(unsigned __val) noexcept : __d(static_cast<unsigned char>(__val)) {}
+    inline constexpr day& operator++()    noexcept { ++__d; return *this; }
+    inline constexpr day  operator++(int) noexcept { day __tmp = *this; ++(*this); return __tmp; }
+    inline constexpr day& operator--()    noexcept { --__d; return *this; }
+    inline constexpr day  operator--(int) noexcept { day __tmp = *this; --(*this); return __tmp; }
+           constexpr day& operator+=(const days& __dd) noexcept;
+           constexpr day& operator-=(const days& __dd) noexcept;
+    explicit inline constexpr operator unsigned() const noexcept { return __d; }
+    inline constexpr bool ok() const noexcept { return __d >= 1 && __d <= 31; }
+  };
+
+
+inline constexpr
+bool operator==(const day& __lhs, const day& __rhs) noexcept
+{ return static_cast<unsigned>(__lhs) == static_cast<unsigned>(__rhs); }
+
+inline constexpr
+bool operator!=(const day& __lhs, const day& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+bool operator< (const day& __lhs, const day& __rhs) noexcept
+{ return static_cast<unsigned>(__lhs) <  static_cast<unsigned>(__rhs); }
+
+inline constexpr
+bool operator> (const day& __lhs, const day& __rhs) noexcept
+{ return __rhs < __lhs; }
+
+inline constexpr
+bool operator<=(const day& __lhs, const day& __rhs) noexcept
+{ return !(__rhs < __lhs);}
+
+inline constexpr
+bool operator>=(const day& __lhs, const day& __rhs) noexcept
+{ return !(__lhs < __rhs); }
+
+inline constexpr
+day operator+ (const day& __lhs, const days& __rhs) noexcept
+{ return day(static_cast<unsigned>(__lhs) + __rhs.count()); }
+
+inline constexpr
+day operator+ (const days& __lhs, const day& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+day operator- (const day& __lhs, const days& __rhs) noexcept
+{ return __lhs + -__rhs; }
+
+inline constexpr
+days operator-(const day& __lhs, const day& __rhs) noexcept
+{ return days(static_cast<int>(static_cast<unsigned>(__lhs)) -
+              static_cast<int>(static_cast<unsigned>(__rhs))); }
+
+inline constexpr day& day::operator+=(const days& __dd) noexcept
+{ *this = *this + __dd; return *this; }
+
+inline constexpr day& day::operator-=(const days& __dd) noexcept
+{ *this = *this - __dd; return *this; }
+
+
+class _LIBCPP_TYPE_VIS month {
+private:
+    unsigned char __m;
+public:
+    month() = default;
+    explicit inline constexpr month(unsigned __val) noexcept : __m(static_cast<unsigned char>(__val)) {}
+    inline constexpr month& operator++()    noexcept { ++__m; return *this; }
+    inline constexpr month  operator++(int) noexcept { month __tmp = *this; ++(*this); return __tmp; }
+    inline constexpr month& operator--()    noexcept { --__m; return *this; }
+    inline constexpr month  operator--(int) noexcept { month __tmp = *this; --(*this); return __tmp; }
+           constexpr month& operator+=(const months& __m1) noexcept;
+           constexpr month& operator-=(const months& __m1) noexcept;
+    explicit inline constexpr operator unsigned() const noexcept { return __m; }
+    inline constexpr bool ok() const noexcept { return __m >= 1 && __m <= 12; }
+};
+
+
+inline constexpr
+bool operator==(const month& __lhs, const month& __rhs) noexcept
+{ return static_cast<unsigned>(__lhs) == static_cast<unsigned>(__rhs); }
+
+inline constexpr
+bool operator!=(const month& __lhs, const month& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+bool operator< (const month& __lhs, const month& __rhs) noexcept
+{ return static_cast<unsigned>(__lhs)  < static_cast<unsigned>(__rhs); }
+
+inline constexpr
+bool operator> (const month& __lhs, const month& __rhs) noexcept
+{ return __rhs < __lhs; }
+
+inline constexpr
+bool operator<=(const month& __lhs, const month& __rhs) noexcept
+{ return !(__rhs < __lhs); }
+
+inline constexpr
+bool operator>=(const month& __lhs, const month& __rhs) noexcept
+{ return !(__lhs < __rhs); }
+
+inline constexpr
+month operator+ (const month& __lhs, const months& __rhs) noexcept
+{
+    auto const __mu = static_cast<long long>(static_cast<unsigned>(__lhs)) + (__rhs.count() - 1);
+    auto const __yr = (__mu >= 0 ? __mu : __mu - 11) / 12;
+    return month{static_cast<unsigned>(__mu - __yr * 12 + 1)};
+}
+
+inline constexpr
+month operator+ (const months& __lhs, const month& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+month operator- (const month& __lhs, const months& __rhs) noexcept
+{ return __lhs + -__rhs; }
+
+inline constexpr
+months operator-(const month& __lhs, const month& __rhs) noexcept
+{
+    auto const __dm = static_cast<unsigned>(__lhs) - static_cast<unsigned>(__rhs);
+    return months(__dm <= 11 ? __dm : __dm + 12);
+}
+
+inline constexpr month& month::operator+=(const months& __dm) noexcept
+{ *this = *this + __dm; return *this; }
+
+inline constexpr month& month::operator-=(const months& __dm) noexcept
+{ *this = *this - __dm; return *this; }
+
+
+class _LIBCPP_TYPE_VIS year {
+private:
+    short __y;
+public:
+    year() = default;
+    explicit inline constexpr year(int __val) noexcept : __y(static_cast<short>(__val)) {}
+
+    inline constexpr year& operator++()    noexcept { ++__y; return *this; };
+    inline constexpr year  operator++(int) noexcept { year __tmp = *this; ++(*this); return __tmp; };
+    inline constexpr year& operator--()    noexcept { --__y; return *this; };
+    inline constexpr year  operator--(int) noexcept { year __tmp = *this; --(*this); return __tmp; };
+           constexpr year& operator+=(const years& __dy) noexcept;
+           constexpr year& operator-=(const years& __dy) noexcept;
+    inline constexpr year operator+() const noexcept { return *this; }
+    inline constexpr year operator-() const noexcept { return year{-__y}; };
+
+    inline constexpr bool is_leap() const noexcept { return __y % 4 == 0 && (__y % 100 != 0 || __y % 400 == 0); }
+    explicit inline constexpr operator int() const noexcept { return __y; }
+           constexpr bool ok() const noexcept;
+    static inline constexpr year min() noexcept { return year{-32767}; }
+    static inline constexpr year max() noexcept { return year{ 32767}; }
+};
+
+
+inline constexpr
+bool operator==(const year& __lhs, const year& __rhs) noexcept
+{ return static_cast<int>(__lhs) == static_cast<int>(__rhs); }
+
+inline constexpr
+bool operator!=(const year& __lhs, const year& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+bool operator< (const year& __lhs, const year& __rhs) noexcept
+{ return static_cast<int>(__lhs)  < static_cast<int>(__rhs); }
+
+inline constexpr
+bool operator> (const year& __lhs, const year& __rhs) noexcept
+{ return __rhs < __lhs; }
+
+inline constexpr
+bool operator<=(const year& __lhs, const year& __rhs) noexcept
+{ return !(__rhs < __lhs); }
+
+inline constexpr
+bool operator>=(const year& __lhs, const year& __rhs) noexcept
+{ return !(__lhs < __rhs); }
+
+inline constexpr
+year operator+ (const year& __lhs, const years& __rhs) noexcept
+{ return year(static_cast<int>(__lhs) + __rhs.count()); }
+
+inline constexpr
+year operator+ (const years& __lhs, const year& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+year operator- (const year& __lhs, const years& __rhs) noexcept
+{ return __lhs + -__rhs; }
+
+inline constexpr
+years operator-(const year& __lhs, const year& __rhs) noexcept
+{ return years{static_cast<int>(__lhs) - static_cast<int>(__rhs)}; }
+
+
+inline constexpr year& year::operator+=(const years& __dy) noexcept
+{ *this = *this + __dy; return *this; }
+
+inline constexpr year& year::operator-=(const years& __dy) noexcept
+{ *this = *this - __dy; return *this; }
+
+inline constexpr bool year::ok() const noexcept
+{ return static_cast<int>(min()) <= __y && __y <= static_cast<int>(max()); }
+
+class _LIBCPP_TYPE_VIS weekday_indexed;
+class _LIBCPP_TYPE_VIS weekday_last;
+
+class _LIBCPP_TYPE_VIS weekday {
+private:
+    unsigned char __wd;
+public:
+  weekday() = default;
+  explicit inline constexpr weekday(unsigned __val) noexcept: __wd(static_cast<unsigned char>(__val)) {}
+//   inline constexpr weekday(const sys_days& dp) noexcept;
+//   explicit constexpr weekday(const local_days& dp) noexcept;
+  inline constexpr weekday& operator++()    noexcept { __wd = (__wd == 6 ? 0 : __wd + 1); return *this; }
+  inline constexpr weekday  operator++(int) noexcept { weekday __tmp = *this; ++(*this); return __tmp; }
+  inline constexpr weekday& operator--()    noexcept { __wd = (__wd == 0 ? 6 : __wd - 1); return *this; }
+  inline constexpr weekday  operator--(int) noexcept { weekday __tmp = *this; --(*this); return __tmp; }
+         constexpr weekday& operator+=(const days& __dd) noexcept;
+         constexpr weekday& operator-=(const days& __dd) noexcept;
+  explicit inline constexpr operator unsigned() const noexcept { return __wd; }
+  inline constexpr bool ok() const noexcept { return __wd <= 6; }
+  constexpr weekday_indexed operator[](unsigned __index) const noexcept;
+  constexpr weekday_last    operator[](last_spec) const noexcept;
+};
+
+inline constexpr
+bool operator==(const weekday& __lhs, const weekday& __rhs) noexcept
+{ return static_cast<unsigned>(__lhs) == static_cast<unsigned>(__rhs); }
+
+inline constexpr
+bool operator!=(const weekday& __lhs, const weekday& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+bool operator< (const weekday& __lhs, const weekday& __rhs) noexcept
+{ return static_cast<unsigned>(__lhs) <  static_cast<unsigned>(__rhs); }
+
+inline constexpr
+bool operator> (const weekday& __lhs, const weekday& __rhs) noexcept
+{ return __rhs < __lhs; }
+
+inline constexpr
+bool operator<=(const weekday& __lhs, const weekday& __rhs) noexcept
+{ return !(__rhs < __lhs);}
+
+inline constexpr
+bool operator>=(const weekday& __lhs, const weekday& __rhs) noexcept
+{ return !(__lhs < __rhs); }
+
+constexpr weekday operator+(const weekday& __lhs, const days& __rhs) noexcept
+{
+    auto const __mu = static_cast<long long>(static_cast<unsigned>(__lhs)) + __rhs.count();
+    auto const __yr = (__mu >= 0 ? __mu : __mu - 6) / 7;
+    return weekday{static_cast<unsigned>(__mu - __yr * 7)};
+}
+
+constexpr weekday operator+(const days& __lhs, const weekday& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+constexpr weekday operator-(const weekday& __lhs, const days& __rhs) noexcept
+{ return __lhs + -__rhs; }
+
+constexpr days operator-(const weekday& __lhs, const weekday& __rhs) noexcept
+{
+    const int __wdu = static_cast<unsigned>(__lhs) - static_cast<unsigned>(__rhs);
+    const int __wk = (__wdu >= 0 ? __wdu : __wdu-6) / 7;
+    return days{__wdu - __wk * 7};
+}
+
+inline constexpr weekday& weekday::operator+=(const days& __dd) noexcept
+{ *this = *this + __dd; return *this; }
+
+inline constexpr weekday& weekday::operator-=(const days& __dd) noexcept
+{ *this = *this - __dd; return *this; }
+
+
+class _LIBCPP_TYPE_VIS weekday_indexed {
+private:
+    _VSTD::chrono::weekday __wd;
+    unsigned char          __idx;
+public:
+    weekday_indexed() = default;
+    inline constexpr weekday_indexed(const _VSTD::chrono::weekday& __wdval, unsigned __idxval) noexcept
+        : __wd{__wdval}, __idx(__idxval) {}
+    inline constexpr _VSTD::chrono::weekday weekday() const noexcept { return __wd; }
+    inline constexpr unsigned                 index() const noexcept { return __idx; }
+    inline constexpr bool ok() const noexcept { return __wd.ok() && __idx >= 1 && __idx <= 5; }
+};
+
+inline constexpr
+bool operator==(const weekday_indexed& __lhs, const weekday_indexed& __rhs) noexcept
+{ return __lhs.weekday() == __rhs.weekday() && __lhs.index() == __rhs.index(); }
+
+inline constexpr
+bool operator!=(const weekday_indexed& __lhs, const weekday_indexed& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+
+class _LIBCPP_TYPE_VIS weekday_last {
+private:
+    _VSTD::chrono::weekday __wd;
+public:
+    explicit constexpr weekday_last(const _VSTD::chrono::weekday& __val) noexcept
+        : __wd{__val} {}
+    constexpr _VSTD::chrono::weekday weekday() const noexcept { return __wd; }
+    constexpr bool ok() const noexcept { return __wd.ok(); }
+};
+
+inline constexpr
+bool operator==(const weekday_last& __lhs, const weekday_last& __rhs) noexcept
+{ return __lhs.weekday() == __rhs.weekday(); }
+
+inline constexpr
+bool operator!=(const weekday_last& __lhs, const weekday_last& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+weekday_indexed weekday::operator[](unsigned __index) const noexcept { return weekday_indexed{*this, __index}; }
+
+inline constexpr 
+weekday_last    weekday::operator[](last_spec) const noexcept { return weekday_last{*this}; }
+
+
+inline constexpr last_spec last{};
+inline constexpr weekday   Sunday{0};
+inline constexpr weekday   Monday{1};
+inline constexpr weekday   Tuesday{2};
+inline constexpr weekday   Wednesday{3};
+inline constexpr weekday   Thursday{4};
+inline constexpr weekday   Friday{5};
+inline constexpr weekday   Saturday{6};
+
+inline constexpr month January{1};
+inline constexpr month February{2};
+inline constexpr month March{3};
+inline constexpr month April{4};
+inline constexpr month May{5};
+inline constexpr month June{6};
+inline constexpr month July{7};
+inline constexpr month August{8};
+inline constexpr month September{9};
+inline constexpr month October{10};
+inline constexpr month November{11};
+inline constexpr month December{12};
+
+
+class _LIBCPP_TYPE_VIS month_day {
+private:
+   chrono::month __m;
+   chrono::day   __d;
+public:
+    month_day() = default;
+    constexpr month_day(const chrono::month& __mval, const chrono::day& __dval) noexcept
+        : __m{__mval}, __d{__dval} {}
+    inline constexpr chrono::month month() const noexcept { return __m; }
+    inline constexpr chrono::day   day()   const noexcept { return __d; }
+    constexpr bool ok() const noexcept;
+};
+
+inline constexpr
+bool month_day::ok() const noexcept
+{
+    if (!__m.ok()) return false;
+    const unsigned __dval = static_cast<unsigned>(__d);
+    if (__dval < 1 || __dval > 31) return false;
+    if (__dval <= 29) return true;
+//  Now we've got either 30 or 31
+    const unsigned __mval = static_cast<unsigned>(__m);
+    if (__mval == 2) return false;
+    if (__mval == 4 || __mval == 6 || __mval == 9 || __mval == 11)
+        return __dval == 30;
+    return true;
+}
+
+inline constexpr
+bool operator==(const month_day& __lhs, const month_day& __rhs) noexcept
+{ return __lhs.month() == __rhs.month() && __lhs.day() == __rhs.day(); }
+
+inline constexpr
+bool operator!=(const month_day& __lhs, const month_day& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+month_day operator/(const month& __lhs, const day& __rhs) noexcept
+{ return month_day{__lhs, __rhs}; }
+
+constexpr
+month_day operator/(const day& __lhs, const month& __rhs) noexcept
+{ return __rhs / __lhs; }
+
+inline constexpr
+month_day operator/(const month& __lhs, int __rhs) noexcept
+{ return __lhs / day(__rhs); }
+
+constexpr
+month_day operator/(int __lhs, const day& __rhs) noexcept
+{ return month(__lhs) / __rhs; }
+
+constexpr
+month_day operator/(const day& __lhs, int __rhs) noexcept
+{ return month(__rhs) / __lhs; }
+
+
+inline constexpr
+bool operator< (const month_day& __lhs, const month_day& __rhs) noexcept
+{ return __lhs.month() != __rhs.month() ? __lhs.month() < __rhs.month() : __lhs.day() < __rhs.day(); }
+
+inline constexpr
+bool operator> (const month_day& __lhs, const month_day& __rhs) noexcept
+{ return __rhs < __lhs; }
+
+inline constexpr
+bool operator<=(const month_day& __lhs, const month_day& __rhs) noexcept
+{ return !(__rhs < __lhs);}
+
+inline constexpr
+bool operator>=(const month_day& __lhs, const month_day& __rhs) noexcept
+{ return !(__lhs < __rhs); }
+
+
+
+class _LIBCPP_TYPE_VIS month_day_last {
+private:
+    chrono::month __m;
+public:
+    explicit constexpr month_day_last(const chrono::month& __val) noexcept
+        : __m{__val} {}
+    inline constexpr chrono::month month() const noexcept { return __m; }
+    inline constexpr bool ok() const noexcept { return __m.ok(); }
+};
+
+inline constexpr
+bool operator==(const month_day_last& __lhs, const month_day_last& __rhs) noexcept
+{ return __lhs.month() == __rhs.month(); }
+
+inline constexpr
+bool operator!=(const month_day_last& __lhs, const month_day_last& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+bool operator< (const month_day_last& __lhs, const month_day_last& __rhs) noexcept
+{ return __lhs.month() < __rhs.month(); }
+
+inline constexpr
+bool operator> (const month_day_last& __lhs, const month_day_last& __rhs) noexcept
+{ return __rhs < __lhs; }
+
+inline constexpr
+bool operator<=(const month_day_last& __lhs, const month_day_last& __rhs) noexcept
+{ return !(__rhs < __lhs);}
+
+inline constexpr
+bool operator>=(const month_day_last& __lhs, const month_day_last& __rhs) noexcept
+{ return !(__lhs < __rhs); }
+
+inline constexpr
+month_day_last operator/(const month& __lhs, last_spec) noexcept
+{ return month_day_last{__lhs}; }
+
+inline constexpr
+month_day_last operator/(last_spec, const month& __rhs) noexcept
+{ return month_day_last{__rhs}; }
+
+inline constexpr
+month_day_last operator/(int __lhs, last_spec) noexcept
+{ return month_day_last{month(__lhs)}; }
+
+inline constexpr
+month_day_last operator/(last_spec, int __rhs) noexcept
+{ return month_day_last{month(__rhs)}; }
+
+
+class _LIBCPP_TYPE_VIS month_weekday {
+private:
+    chrono::month __m;
+    chrono::weekday_indexed __wdi;
+public:
+    month_weekday() = default;
+    constexpr month_weekday(const chrono::month& __mval, const chrono::weekday_indexed& __wdival) noexcept
+        : __m{__mval}, __wdi{__wdival} {}
+    inline constexpr chrono::month                     month() const noexcept { return __m; }
+    inline constexpr chrono::weekday_indexed weekday_indexed() const noexcept { return __wdi; }
+    inline constexpr bool                                 ok() const noexcept { return __m.ok() && __wdi.ok(); }
+};
+
+inline constexpr
+bool operator==(const month_weekday& __lhs, const month_weekday& __rhs) noexcept
+{ return __lhs.month() == __rhs.month() && __lhs.weekday_indexed() == __rhs.weekday_indexed(); }
+
+inline constexpr
+bool operator!=(const month_weekday& __lhs, const month_weekday& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+month_weekday operator/(const month& __lhs, const weekday_indexed& __rhs) noexcept
+{ return month_weekday{__lhs, __rhs}; }
+
+inline constexpr
+month_weekday operator/(int __lhs, const weekday_indexed& __rhs) noexcept
+{ return month_weekday{month(__lhs), __rhs}; }
+
+inline constexpr
+month_weekday operator/(const weekday_indexed& __lhs, const month& __rhs) noexcept
+{ return month_weekday{__rhs, __lhs}; }
+
+inline constexpr
+month_weekday operator/(const weekday_indexed& __lhs, int __rhs) noexcept
+{ return month_weekday{month(__rhs), __lhs}; }
+
+
+class _LIBCPP_TYPE_VIS month_weekday_last {
+    chrono::month        __m;
+    chrono::weekday_last __wdl;
+  public:
+    constexpr month_weekday_last(const chrono::month& __mval, const chrono::weekday_last& __wdlval) noexcept
+        : __m{__mval}, __wdl{__wdlval} {}
+    inline constexpr chrono::month               month() const noexcept { return __m; }
+    inline constexpr chrono::weekday_last weekday_last() const noexcept { return __wdl; }
+    inline constexpr bool                           ok() const noexcept { return __m.ok() && __wdl.ok(); }
+};
+
+inline constexpr
+bool operator==(const month_weekday_last& __lhs, const month_weekday_last& __rhs) noexcept
+{ return __lhs.month() == __rhs.month() && __lhs.weekday_last() == __rhs.weekday_last(); }
+
+inline constexpr
+bool operator!=(const month_weekday_last& __lhs, const month_weekday_last& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+
+inline constexpr
+month_weekday_last operator/(const month& __lhs, const weekday_last& __rhs) noexcept
+{ return month_weekday_last{__lhs, __rhs}; }
+
+inline constexpr
+month_weekday_last operator/(int __lhs, const weekday_last& __rhs) noexcept
+{ return month_weekday_last{month(__lhs), __rhs}; }
+
+inline constexpr
+month_weekday_last operator/(const weekday_last& __lhs, const month& __rhs) noexcept
+{ return month_weekday_last{__rhs, __lhs}; }
+
+inline constexpr
+month_weekday_last operator/(const weekday_last& __lhs, int __rhs) noexcept
+{ return month_weekday_last{month(__rhs), __lhs}; }
+
+
+class _LIBCPP_TYPE_VIS year_month {
+    chrono::year  __y;
+    chrono::month __m;
+public:
+    year_month() = default;
+    constexpr year_month(const chrono::year& __yval, const chrono::month& __mval) noexcept
+        : __y{__yval}, __m{__mval} {}
+    inline constexpr chrono::year  year()  const noexcept { return __y; }
+    inline constexpr chrono::month month() const noexcept { return __m; }
+    inline constexpr year_month& operator+=(const months& __dm) noexcept { this->__m += __dm; return *this; }
+    inline constexpr year_month& operator-=(const months& __dm) noexcept { this->__m -= __dm; return *this; }
+    inline constexpr year_month& operator+=(const years& __dy)  noexcept { this->__y += __dy; return *this; }
+    inline constexpr year_month& operator-=(const years& __dy)  noexcept { this->__y -= __dy; return *this; }
+    inline constexpr bool ok() const noexcept { return __y.ok() && __m.ok(); }
+};
+
+inline constexpr
+year_month operator/(const year& __y, const month& __m) noexcept { return year_month{__y, __m}; }
+
+inline constexpr
+year_month operator/(const year& __y, int __m) noexcept { return year_month{__y, month(__m)}; }
+
+inline constexpr
+bool operator==(const year_month& __lhs, const year_month& __rhs) noexcept
+{ return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month(); }
+
+inline constexpr
+bool operator!=(const year_month& __lhs, const year_month& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+bool operator< (const year_month& __lhs, const year_month& __rhs) noexcept
+{ return __lhs.year() != __rhs.year() ? __lhs.year() < __rhs.year() : __lhs.month() < __rhs.month(); }
+
+inline constexpr
+bool operator> (const year_month& __lhs, const year_month& __rhs) noexcept
+{ return __rhs < __lhs; }
+
+inline constexpr
+bool operator<=(const year_month& __lhs, const year_month& __rhs) noexcept
+{ return !(__rhs < __lhs);}
+
+inline constexpr
+bool operator>=(const year_month& __lhs, const year_month& __rhs) noexcept
+{ return !(__lhs < __rhs); }
+
+constexpr year_month operator+(const year_month& __lhs, const months& __rhs) noexcept
+{
+    int __dmi = static_cast<int>(static_cast<unsigned>(__lhs.month())) - 1 + __rhs.count();
+    const int __dy = (__dmi >= 0 ? __dmi : __dmi-11) / 12;
+    __dmi = __dmi - __dy * 12 + 1;
+    return (__lhs.year() + years(__dy)) / month(static_cast<unsigned>(__dmi));
+}
+
+constexpr year_month operator+(const months& __lhs, const year_month& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+constexpr year_month operator+(const year_month& __lhs, const years& __rhs) noexcept
+{ return (__lhs.year() + __rhs) / __lhs.month(); }
+
+constexpr year_month operator+(const years& __lhs, const year_month& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+constexpr months     operator-(const year_month& __lhs, const year_month& __rhs) noexcept
+{ return (__lhs.year() - __rhs.year()) + months(static_cast<unsigned>(__lhs.month()) - static_cast<unsigned>(__rhs.month())); }
+
+constexpr year_month operator-(const year_month& __lhs, const months& __rhs) noexcept
+{ return __lhs + -__rhs; }
+
+constexpr year_month operator-(const year_month& __lhs, const years& __rhs) noexcept
+{ return __lhs + -__rhs; }
+
+
+class _LIBCPP_TYPE_VIS year_month_day {
+private:
+    chrono::year  __y;
+    chrono::month __m;
+    chrono::day   __d;
+public:
+     year_month_day() = default;
+     inline constexpr year_month_day(
+            const chrono::year& __yval, const chrono::month& __mval, const chrono::day& __dval) noexcept
+            : __y{__yval}, __m{__mval}, __d{__dval} {}  
+//   inline constexpr year_month_day(const year_month_day_last& __ymdl) noexcept;
+//   inline constexpr year_month_day(const sys_days& dp) noexcept;
+//   inline explicit constexpr year_month_day(const local_days& dp) noexcept;
+            constexpr year_month_day& operator+=(const months& __dm) noexcept;
+            constexpr year_month_day& operator-=(const months& __dm) noexcept;
+            constexpr year_month_day& operator+=(const years& __dy)  noexcept;
+            constexpr year_month_day& operator-=(const years& __dy)  noexcept;
+     inline constexpr chrono::year  year()  const noexcept { return __y; }
+     inline constexpr chrono::month month() const noexcept { return __m; }
+     inline constexpr chrono::day   day()   const noexcept  { return __d; }
+//   inline constexpr operator            sys_days() const noexcept;
+//   inline explicit constexpr operator local_days() const noexcept;
+
+//   TODO: This is not quite correct; requires the calendar bits to do right
+//   d_ is in the range [1d, (y_/m_/last).day()],
+     inline constexpr bool ok() const noexcept { return __y.ok() && __m.ok() && __d.ok(); }
+};
+
+inline constexpr
+bool operator==(const year_month_day& __lhs, const year_month_day& __rhs) noexcept
+{ return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month() && __lhs.day() == __rhs.day(); }
+
+inline constexpr
+bool operator!=(const year_month_day& __lhs, const year_month_day& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+bool operator< (const year_month_day& __lhs, const year_month_day& __rhs) noexcept
+{
+    if (__lhs.year() < __rhs.year()) return true;
+    if (__lhs.year() > __rhs.year()) return false;
+    if (__lhs.month() < __rhs.month()) return true;
+    if (__lhs.month() > __rhs.month()) return false;
+    return __lhs.day() < __rhs.day();
+}
+
+inline constexpr
+bool operator> (const year_month_day& __lhs, const year_month_day& __rhs) noexcept
+{ return __rhs < __lhs; }
+
+inline constexpr
+bool operator<=(const year_month_day& __lhs, const year_month_day& __rhs) noexcept
+{ return !(__rhs < __lhs);}
+
+inline constexpr
+bool operator>=(const year_month_day& __lhs, const year_month_day& __rhs) noexcept
+{ return !(__lhs < __rhs); }
+
+inline constexpr
+year_month_day operator/(const year_month& __lhs, const day& __rhs) noexcept
+{ return year_month_day{__lhs.year(), __lhs.month(), __rhs}; }
+
+inline constexpr
+year_month_day operator/(const year_month& __lhs, int __rhs) noexcept
+{ return __lhs / day(__rhs); }
+
+inline constexpr
+year_month_day operator/(const year& __lhs, const month_day& __rhs) noexcept
+{ return __lhs / __rhs.month() / __rhs.day(); }
+
+inline constexpr
+year_month_day operator/(int __lhs, const month_day& __rhs) noexcept
+{ return year(__lhs) / __rhs; }
+
+inline constexpr
+year_month_day operator/(const month_day& __lhs, const year& __rhs) noexcept
+{ return __rhs / __lhs; }
+
+inline constexpr
+year_month_day operator/(const month_day& __lhs, int __rhs) noexcept
+{ return year(__rhs) / __lhs; }
+
+
+inline constexpr
+year_month_day operator+(const year_month_day& __lhs, const months& __rhs) noexcept
+{ return (__lhs.year()/__lhs.month() + __rhs)/__lhs.day(); }
+
+inline constexpr
+year_month_day operator+(const months& __lhs, const year_month_day& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+year_month_day operator-(const year_month_day& __lhs, const months& __rhs) noexcept
+{ return __lhs + -__rhs; }
+
+inline constexpr
+year_month_day operator+(const year_month_day& __lhs, const years& __rhs) noexcept
+{ return (__lhs.year() + __rhs) / __lhs.month() / __lhs.day(); }
+
+inline constexpr
+year_month_day operator+(const years& __lhs, const year_month_day& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+year_month_day operator-(const year_month_day& __lhs, const years& __rhs) noexcept
+{ return __lhs + -__rhs; }
+
+inline constexpr year_month_day& year_month_day::operator+=(const months& __dm) noexcept { *this = *this + __dm; return *this; }
+inline constexpr year_month_day& year_month_day::operator-=(const months& __dm) noexcept { *this = *this - __dm; return *this; }
+inline constexpr year_month_day& year_month_day::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
+inline constexpr year_month_day& year_month_day::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }
+
+class _LIBCPP_TYPE_VIS year_month_day_last {
+private:
+    chrono::year           __y;
+    chrono::month_day_last __mdl;
+public:
+     constexpr year_month_day_last(const year& __yval, const month_day_last& __mdlval) noexcept
+        : __y{__yval}, __mdl{__mdlval} {}
+
+     constexpr year_month_day_last& operator+=(const months& __m) noexcept;
+     constexpr year_month_day_last& operator-=(const months& __m) noexcept;
+     constexpr year_month_day_last& operator+=(const years& __y)  noexcept;
+     constexpr year_month_day_last& operator-=(const years& __y)  noexcept;
+
+     constexpr chrono::year           year()           const noexcept { return __y; }
+     constexpr chrono::month          month()          const noexcept { return __mdl.month(); }
+     constexpr chrono::month_day_last month_day_last() const noexcept { return __mdl; }
+//   constexpr chrono::day            day()            const noexcept;
+//   constexpr          operator sys_days()   const noexcept;
+//   explicit constexpr operator local_days() const noexcept;
+     constexpr bool ok() const noexcept { return __y.ok() && __mdl.ok(); }
+};
+
+inline constexpr
+bool operator==(const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
+{ return __lhs.year() == __rhs.year() && __lhs.month_day_last() == __rhs.month_day_last(); }
+
+inline constexpr
+bool operator!=(const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+bool operator< (const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
+{
+    if (__lhs.year() < __rhs.year()) return true;
+    if (__lhs.year() > __rhs.year()) return false;
+    return __lhs.month_day_last() < __rhs.month_day_last();
+}
+
+inline constexpr
+bool operator> (const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
+{ return __rhs < __lhs; }
+
+inline constexpr
+bool operator<=(const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
+{ return !(__rhs < __lhs);}
+
+inline constexpr
+bool operator>=(const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
+{ return !(__lhs < __rhs); }
+
+inline constexpr year_month_day_last operator/(const year_month& __lhs, last_spec) noexcept
+{ return year_month_day_last{__lhs.year(), month_day_last{__lhs.month()}}; }
+
+inline constexpr year_month_day_last operator/(const year& __lhs, const month_day_last& __rhs) noexcept
+{ return year_month_day_last{__lhs, __rhs}; }
+
+inline constexpr year_month_day_last operator/(int __lhs, const month_day_last& __rhs) noexcept
+{ return year_month_day_last{year{__lhs}, __rhs}; }
+
+inline constexpr year_month_day_last operator/(const month_day_last& __lhs, const year& __rhs) noexcept
+{ return __rhs / __lhs; }
+
+inline constexpr year_month_day_last operator/(const month_day_last& __lhs, int __rhs) noexcept
+{ return year{__rhs} / __lhs; }
+
+
+inline constexpr
+year_month_day_last operator+(const year_month_day_last& __lhs, const months& __rhs) noexcept
+{ return (__lhs.year() / __lhs.month() + __rhs) / last; }
+
+inline constexpr
+year_month_day_last operator+(const months& __lhs, const year_month_day_last& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+year_month_day_last operator-(const year_month_day_last& __lhs, const months& __rhs) noexcept
+{ return __lhs + (-__rhs); }
+
+inline constexpr
+year_month_day_last operator+(const year_month_day_last& __lhs, const years& __rhs) noexcept
+{ return year_month_day_last{__lhs.year() + __rhs, __lhs.month_day_last()}; }
+
+inline constexpr
+year_month_day_last operator+(const years& __lhs, const year_month_day_last& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+year_month_day_last operator-(const year_month_day_last& __lhs, const years& __rhs) noexcept
+{ return __lhs + (-__rhs); }
+
+inline constexpr year_month_day_last& year_month_day_last::operator+=(const months& __dm) noexcept { *this = *this + __dm; return *this; }
+inline constexpr year_month_day_last& year_month_day_last::operator-=(const months& __dm) noexcept { *this = *this - __dm; return *this; }
+inline constexpr year_month_day_last& year_month_day_last::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
+inline constexpr year_month_day_last& year_month_day_last::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }
+
+class _LIBCPP_TYPE_VIS year_month_weekday {
+    chrono::year            __y;
+    chrono::month           __m;
+    chrono::weekday_indexed __wdi;
+public:
+    year_month_weekday() = default;
+    constexpr year_month_weekday(const chrono::year& __yval, const chrono::month& __mval,
+                               const chrono::weekday_indexed& __wdival) noexcept
+        : __y{__yval}, __m{__mval}, __wdi{__wdival} {}
+//  constexpr year_month_weekday(const sys_days& dp) noexcept;
+//  explicit constexpr year_month_weekday(const local_days& dp) noexcept;
+    constexpr year_month_weekday& operator+=(const months& m) noexcept;
+    constexpr year_month_weekday& operator-=(const months& m) noexcept;
+    constexpr year_month_weekday& operator+=(const years& y)  noexcept;
+    constexpr year_month_weekday& operator-=(const years& y)  noexcept;
+
+    inline constexpr chrono::year                       year() const noexcept { return __y; }
+    inline constexpr chrono::month                     month() const noexcept { return __m; }
+    inline constexpr chrono::weekday                 weekday() const noexcept { return __wdi.weekday(); }
+    inline constexpr unsigned                          index() const noexcept { return __wdi.index(); }
+    inline constexpr chrono::weekday_indexed weekday_indexed() const noexcept { return __wdi; }
+
+//  constexpr          operator sys_days()   const noexcept;
+//  explicit constexpr operator local_days() const noexcept;
+    inline constexpr bool ok() const noexcept
+    {
+        if (!__y.ok() || !__m.ok() || !__wdi.ok()) return false;
+    //  TODO: make sure it's a valid date
+        return true;
+    }
+};
+
+inline constexpr
+bool operator==(const year_month_weekday& __lhs, const year_month_weekday& __rhs) noexcept
+{ return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month() && __lhs.weekday_indexed() == __rhs.weekday_indexed(); }
+
+inline constexpr
+bool operator!=(const year_month_weekday& __lhs, const year_month_weekday& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+inline constexpr
+year_month_weekday operator/(const year_month& __lhs, const weekday_indexed& __rhs) noexcept
+{ return year_month_weekday{__lhs.year(), __lhs.month(), __rhs}; }
+
+inline constexpr
+year_month_weekday operator/(const year& __lhs, const month_weekday& __rhs) noexcept
+{ return year_month_weekday{__lhs, __rhs.month(), __rhs.weekday_indexed()}; }
+
+inline constexpr
+year_month_weekday operator/(int __lhs, const month_weekday& __rhs) noexcept
+{ return year(__lhs) / __rhs; }
+
+inline constexpr
+year_month_weekday operator/(const month_weekday& __lhs, const year& __rhs) noexcept
+{ return __rhs / __lhs; }
+
+inline constexpr
+year_month_weekday operator/(const month_weekday& __lhs, int __rhs) noexcept
+{ return year(__rhs) / __lhs; }
+
+
+inline constexpr
+year_month_weekday operator+(const year_month_weekday& __lhs, const months& __rhs) noexcept
+{ return (__lhs.year() / __lhs.month() + __rhs) / __lhs.weekday_indexed(); }
+
+inline constexpr
+year_month_weekday operator+(const months& __lhs, const year_month_weekday& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+year_month_weekday operator-(const year_month_weekday& __lhs, const months& __rhs) noexcept
+{ return __lhs + (-__rhs); }
+
+inline constexpr
+year_month_weekday operator+(const year_month_weekday& __lhs, const years& __rhs) noexcept
+{ return year_month_weekday{__lhs.year() + __rhs, __lhs.month(), __lhs.weekday_indexed()}; }
+
+inline constexpr
+year_month_weekday operator+(const years& __lhs, const year_month_weekday& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+year_month_weekday operator-(const year_month_weekday& __lhs, const years& __rhs) noexcept
+{ return __lhs + (-__rhs); }
+
+
+inline constexpr year_month_weekday& year_month_weekday::operator+=(const months& __dm) noexcept { *this = *this + __dm; return *this; }
+inline constexpr year_month_weekday& year_month_weekday::operator-=(const months& __dm) noexcept { *this = *this - __dm; return *this; }
+inline constexpr year_month_weekday& year_month_weekday::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
+inline constexpr year_month_weekday& year_month_weekday::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }
+
+class _LIBCPP_TYPE_VIS year_month_weekday_last {
+private:
+    chrono::year         __y;
+    chrono::month        __m;
+    chrono::weekday_last __wdl;
+public:
+    constexpr year_month_weekday_last(const chrono::year& __yval, const chrono::month& __mval,
+                                      const chrono::weekday_last& __wdlval) noexcept
+                : __y{__yval}, __m{__mval}, __wdl{__wdlval} {}
+    constexpr year_month_weekday_last& operator+=(const months& __dm) noexcept;
+    constexpr year_month_weekday_last& operator-=(const months& __dm) noexcept;
+    constexpr year_month_weekday_last& operator+=(const years& __dy)  noexcept;
+    constexpr year_month_weekday_last& operator-=(const years& __dy)  noexcept;
+
+    inline constexpr chrono::year                 year() const noexcept { return __y; }
+    inline constexpr chrono::month               month() const noexcept { return __m; }
+    inline constexpr chrono::weekday           weekday() const noexcept { return __wdl.weekday(); }
+    inline constexpr chrono::weekday_last weekday_last() const noexcept { return __wdl; }
+//  constexpr          operator sys_days()   const noexcept;
+//  explicit constexpr operator local_days() const noexcept;
+    inline constexpr bool ok() const noexcept { return __y.ok() && __m.ok() && __wdl.ok(); }
+};
+
+inline constexpr
+bool operator==(const year_month_weekday_last& __lhs, const year_month_weekday_last& __rhs) noexcept
+{ return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month() && __lhs.weekday_last() == __rhs.weekday_last(); }
+
+inline constexpr
+bool operator!=(const year_month_weekday_last& __lhs, const year_month_weekday_last& __rhs) noexcept
+{ return !(__lhs == __rhs); }
+
+
+inline constexpr
+year_month_weekday_last operator/(const year_month& __lhs, const weekday_last& __rhs) noexcept
+{ return year_month_weekday_last{__lhs.year(), __lhs.month(), __rhs}; }
+
+inline constexpr
+year_month_weekday_last operator/(const year& __lhs, const month_weekday_last& __rhs) noexcept
+{ return year_month_weekday_last{__lhs, __rhs.month(), __rhs.weekday_last()}; }
+
+inline constexpr
+year_month_weekday_last operator/(int __lhs, const month_weekday_last& __rhs) noexcept
+{ return year(__lhs) / __rhs; }
+
+inline constexpr
+year_month_weekday_last operator/(const month_weekday_last& __lhs, const year& __rhs) noexcept
+{ return __rhs / __lhs; }
+
+inline constexpr
+year_month_weekday_last operator/(const month_weekday_last& __lhs, int __rhs) noexcept
+{ return year(__rhs) / __lhs; }  
+
+
+inline constexpr
+year_month_weekday_last operator+(const year_month_weekday_last& __lhs, const months& __rhs) noexcept
+{ return (__lhs.year() / __lhs.month() + __rhs) / __lhs.weekday_last(); }
+
+inline constexpr
+year_month_weekday_last operator+(const months& __lhs, const year_month_weekday_last& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+year_month_weekday_last operator-(const year_month_weekday_last& __lhs, const months& __rhs) noexcept
+{ return __lhs + (-__rhs); }
+
+inline constexpr
+year_month_weekday_last operator+(const year_month_weekday_last& __lhs, const years& __rhs) noexcept
+{ return year_month_weekday_last{__lhs.year() + __rhs, __lhs.month(), __lhs.weekday_last()}; }
+
+inline constexpr
+year_month_weekday_last operator+(const years& __lhs, const year_month_weekday_last& __rhs) noexcept
+{ return __rhs + __lhs; }
+
+inline constexpr
+year_month_weekday_last operator-(const year_month_weekday_last& __lhs, const years& __rhs) noexcept
+{ return __lhs + (-__rhs); }
+
+inline constexpr year_month_weekday_last& year_month_weekday_last::operator+=(const months& __dm) noexcept { *this = *this + __dm; return *this; }
+inline constexpr year_month_weekday_last& year_month_weekday_last::operator-=(const months& __dm) noexcept { *this = *this - __dm; return *this; }
+inline constexpr year_month_weekday_last& year_month_weekday_last::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
+inline constexpr year_month_weekday_last& year_month_weekday_last::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }
+
+#endif // _LIBCPP_STD_VER > 17
 } // chrono
 
 #if _LIBCPP_STD_VER > 11
@@ -1648,6 +2668,17 @@ inline namespace literals
         return chrono::duration<long double, nano> (__ns);
     }
 
+#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CXX20_CHRONO_LITERALS)
+    constexpr chrono::day operator ""d(unsigned long long __d) noexcept
+    {
+        return chrono::day(static_cast<unsigned>(__d));
+    }
+ 
+    constexpr chrono::year operator ""y(unsigned long long __y) noexcept
+    {
+        return chrono::year(static_cast<int>(__y));
+    }
+#endif
 }}
 
 namespace chrono { // hoist the literals into namespace std::chrono
diff --git a/test/std/utilities/time/days.pass.cpp b/test/std/utilities/time/days.pass.cpp
new file mode 100644
index 000000000..3954e986a
--- /dev/null
+++ b/test/std/utilities/time/days.pass.cpp
@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// using days = duration<signed integer type of at least 25 bits, ratio_multiply<ratio<24>, hours::period>>;
+
+#include <chrono>
+#include <type_traits>
+#include <limits>
+
+int main()
+{
+    typedef std::chrono::days D;
+    typedef D::rep Rep;
+    typedef D::period Period;
+    static_assert(std::is_signed<Rep>::value, "");
+    static_assert(std::is_integral<Rep>::value, "");
+    static_assert(std::numeric_limits<Rep>::digits >= 25, "");
+    static_assert(std::is_same_v<Period, std::ratio_multiply<std::ratio<24>, std::chrono::hours::period>>, "");
+}
diff --git a/test/std/utilities/time/months.pass.cpp b/test/std/utilities/time/months.pass.cpp
new file mode 100644
index 000000000..9a48b0a19
--- /dev/null
+++ b/test/std/utilities/time/months.pass.cpp
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// using months = duration<signed integer type of at least 20 bits, ratio_divide<years::period, ratio<12>>>;
+
+
+#include <chrono>
+#include <type_traits>
+#include <limits>
+
+int main()
+{
+    typedef std::chrono::months D;
+    typedef D::rep Rep;
+    typedef D::period Period;
+    static_assert(std::is_signed<Rep>::value, "");
+    static_assert(std::is_integral<Rep>::value, "");
+    static_assert(std::numeric_limits<Rep>::digits >= 20, "");
+    static_assert(std::is_same_v<Period, std::ratio_divide<std::chrono::years::period, std::ratio<12>>>, "");
+}
diff --git a/test/std/utilities/time/time.cal/euclidian.h b/test/std/utilities/time/time.cal/euclidian.h
new file mode 100644
index 000000000..f2dc28b36
--- /dev/null
+++ b/test/std/utilities/time/time.cal/euclidian.h
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+
+//  Assumption: minValue < maxValue
+//  Assumption: minValue <= rhs <= maxValue
+//  Assumption: minValue <= lhs <= maxValue
+//  Assumption: minValue >= 0
+template <typename T, T minValue, T maxValue>
+T euclidian_addition(T rhs, T lhs)
+{
+    const T modulus = maxValue - minValue + 1;
+    T ret = rhs + lhs;
+    if (ret > maxValue) 
+        ret -= modulus;
+    return ret;
+}
+
+//  Assumption: minValue < maxValue
+//  Assumption: minValue <= rhs <= maxValue
+//  Assumption: minValue <= lhs <= maxValue
+//  Assumption: minValue >= 0
+template <typename T, T minValue, T maxValue>
+T euclidian_subtraction(T lhs, T rhs)
+{
+    const T modulus = maxValue - minValue + 1;
+    T ret = lhs - rhs;
+    if (ret < minValue) 
+        ret += modulus;
+    if (ret > maxValue)     // this can happen if T is unsigned
+        ret += modulus;
+    return ret;
+}
+
diff --git a/test/std/utilities/time/time.cal/nothing_to_do.pass.cpp b/test/std/utilities/time/time.cal/nothing_to_do.pass.cpp
new file mode 100644
index 000000000..b58f5c55b
--- /dev/null
+++ b/test/std/utilities/time/time.cal/nothing_to_do.pass.cpp
@@ -0,0 +1,12 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+int main()
+{
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/ctor.pass.cpp
new file mode 100644
index 000000000..c2c2eba87
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/ctor.pass.cpp
@@ -0,0 +1,46 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class day;
+
+//                     day() = default;
+//  explicit constexpr day(unsigned d) noexcept;
+//  explicit constexpr operator unsigned() const noexcept;
+
+//  Effects: Constructs an object of type day by initializing d_ with d.
+//    The value held is unspecified if d is not in the range [0, 255].
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using day = std::chrono::day;
+
+    ASSERT_NOEXCEPT(day{});
+    ASSERT_NOEXCEPT(day(0U));
+    ASSERT_NOEXCEPT(static_cast<unsigned>(day(0U)));
+    
+    constexpr day d0{};
+    static_assert(static_cast<unsigned>(d0) == 0, "");
+    
+    constexpr day d1{1};
+    static_assert(static_cast<unsigned>(d1) == 1, "");
+    
+    for (unsigned i = 0; i <= 255; ++i)
+    {
+        day day(i);
+        assert(static_cast<unsigned>(day) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/decrement.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/decrement.pass.cpp
new file mode 100644
index 000000000..819709a89
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/decrement.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class day;
+
+//  constexpr day& operator--() noexcept;
+//  constexpr day operator--(int) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D>
+constexpr bool testConstexpr()
+{
+    D d1{10};
+    if (static_cast<unsigned>(--d1) != 9) return false;
+    if (static_cast<unsigned>(d1--) != 9) return false;
+    if (static_cast<unsigned>(d1)   != 8) return false;
+    return true;
+}
+
+int main()
+{
+    using day = std::chrono::day;
+    ASSERT_NOEXCEPT(--(std::declval<day&>())  );
+    ASSERT_NOEXCEPT(  (std::declval<day&>())--);
+
+    ASSERT_SAME_TYPE(day , decltype(  std::declval<day&>()--));
+    ASSERT_SAME_TYPE(day&, decltype(--std::declval<day&>()  ));
+
+    static_assert(testConstexpr<day>(), "");
+
+    for (unsigned i = 10; i <= 20; ++i)
+    {
+        day day(i);
+        assert(static_cast<unsigned>(--day) == i - 1);
+        assert(static_cast<unsigned>(day--) == i - 1);
+        assert(static_cast<unsigned>(day)   == i - 2);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/increment.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/increment.pass.cpp
new file mode 100644
index 000000000..323bf8bfe
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/increment.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class day;
+
+//  constexpr day& operator++() noexcept;
+//  constexpr day operator++(int) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D>
+constexpr bool testConstexpr()
+{
+    D d1{1};
+    if (static_cast<unsigned>(++d1) != 2) return false;
+    if (static_cast<unsigned>(d1++) != 2) return false;
+    if (static_cast<unsigned>(d1)   != 3) return false;
+    return true;
+}
+
+int main()
+{
+    using day = std::chrono::day;
+    ASSERT_NOEXCEPT(++(std::declval<day&>())  );
+    ASSERT_NOEXCEPT(  (std::declval<day&>())++);
+
+    ASSERT_SAME_TYPE(day , decltype(  std::declval<day&>()++));
+    ASSERT_SAME_TYPE(day&, decltype(++std::declval<day&>()  ));
+    
+    static_assert(testConstexpr<day>(), "");
+
+    for (unsigned i = 10; i <= 20; ++i)
+    {
+        day day(i);
+        assert(static_cast<unsigned>(++day) == i + 1);
+        assert(static_cast<unsigned>(day++) == i + 1);
+        assert(static_cast<unsigned>(day)   == i + 2);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/ok.pass.cpp
new file mode 100644
index 000000000..c3510fee3
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/ok.pass.cpp
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class day;
+
+// constexpr bool ok() const noexcept;
+//  Returns: 1 <= d_ && d_ <= 31
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using day = std::chrono::day;
+    ASSERT_NOEXCEPT(                std::declval<const day>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const day>().ok()));
+
+    static_assert(!day{0}.ok(), "");
+    static_assert( day{1}.ok(), "");
+
+    assert(!day{0}.ok());
+    for (unsigned i = 1; i <= 31; ++i)
+        assert(day{i}.ok());
+    for (unsigned i = 32; i <= 255; ++i)
+        assert(!day{i}.ok());
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/plus_minus_equal.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/plus_minus_equal.pass.cpp
new file mode 100644
index 000000000..f8fd89aa8
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.members/plus_minus_equal.pass.cpp
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class day;
+
+// constexpr day& operator+=(const days& d) noexcept;
+// constexpr day& operator-=(const days& d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr()
+{
+    D d1{1};
+    if (static_cast<unsigned>(d1 += Ds{ 1}) !=  2) return false;
+    if (static_cast<unsigned>(d1 += Ds{ 2}) !=  4) return false;
+    if (static_cast<unsigned>(d1 += Ds{22}) != 26) return false;
+    if (static_cast<unsigned>(d1 -= Ds{ 1}) != 25) return false;
+    if (static_cast<unsigned>(d1 -= Ds{ 2}) != 23) return false;
+    if (static_cast<unsigned>(d1 -= Ds{22}) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using day  = std::chrono::day;
+    using days = std::chrono::days;
+
+    ASSERT_NOEXCEPT(std::declval<day&>() += std::declval<days>());
+    ASSERT_NOEXCEPT(std::declval<day&>() -= std::declval<days>());
+
+    ASSERT_SAME_TYPE(day&, decltype(std::declval<day&>() += std::declval<days>()));
+    ASSERT_SAME_TYPE(day&, decltype(std::declval<day&>() -= std::declval<days>()));
+    
+    static_assert(testConstexpr<day, days>(), "");
+
+    for (unsigned i = 0; i <= 10; ++i)
+    {
+        day day(i);
+        assert(static_cast<unsigned>(day += days{22}) == i + 22);
+        assert(static_cast<unsigned>(day)             == i + 22);
+        assert(static_cast<unsigned>(day -= days{12}) == i + 10);
+        assert(static_cast<unsigned>(day)             == i + 10);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..a5a25b760
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class day;
+
+// constexpr bool operator==(const day& x, const day& y) noexcept;
+//   Returns: unsigned{x} == unsigned{y}.
+// constexpr bool operator<(const day& x, const day& y) noexcept;
+//   Returns: unsigned{x} < unsigned{y}.
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using day = std::chrono::day;
+
+    AssertComparisons6AreNoexcept<day>();
+    AssertComparisons6ReturnBool<day>();
+    
+    static_assert(testComparisons6Values<day>(0U, 0U), "");
+    static_assert(testComparisons6Values<day>(0U, 1U), "");
+    
+//  Some 'ok' values as well
+    static_assert(testComparisons6Values<day>( 5U,  5U), "");
+    static_assert(testComparisons6Values<day>( 5U, 10U), "");
+    
+    for (unsigned i = 1; i < 10; ++i)
+        for (unsigned j = 1; j < 10; ++j)
+            assert(testComparisons6Values<day>(i, j));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/literals.fail.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/literals.fail.cpp
new file mode 100644
index 000000000..0b2a09049
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/literals.fail.cpp
@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-5, clang-6
+// UNSUPPORTED: apple-clang-6, apple-clang-7, apple-clang-8, apple-clang-9
+
+// <chrono>
+// class day;
+
+// constexpr day operator""d(unsigned long long d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using day = std::chrono::day;
+    day d1 = 4d; // expected-error-re {{no matching literal operator for call to 'operator""d' {{.*}}}}
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/literals.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/literals.pass.cpp
new file mode 100644
index 000000000..0911b43b5
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/literals.pass.cpp
@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-5, clang-6
+// UNSUPPORTED: apple-clang-6, apple-clang-7, apple-clang-8, apple-clang-9
+
+// <chrono>
+// class day;
+
+// constexpr day operator""d(unsigned long long d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    {
+    using namespace std::chrono;
+    ASSERT_NOEXCEPT(               4d);
+    ASSERT_SAME_TYPE(day, decltype(4d));
+
+    static_assert( 7d == day(7), "");
+    day d1 = 4d;
+    assert (d1 == day(4));
+}
+
+    {
+    using namespace std::literals;
+    ASSERT_NOEXCEPT(                            4d);
+    ASSERT_SAME_TYPE(std::chrono::day, decltype(4d));
+
+    static_assert( 7d == std::chrono::day(7), "");
+
+    std::chrono::day d1 = 4d;
+    assert (d1 == std::chrono::day(4));
+    }
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/minus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/minus.pass.cpp
new file mode 100644
index 000000000..53697c101
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/minus.pass.cpp
@@ -0,0 +1,58 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class day;
+
+// constexpr day operator-(const day& x, const days& y) noexcept;
+//   Returns: x + -y.
+//
+// constexpr days operator-(const day& x, const day& y) noexcept;
+//   Returns: days{int(unsigned{x}) - int(unsigned{y}).
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr()
+{
+    D d{23};
+    Ds offset{6};
+    if (d - offset != D{17}) return false;
+    if (d - D{17} != offset) return false;
+    return true;
+}
+
+int main()
+{
+    using day  = std::chrono::day;
+    using days = std::chrono::days;
+
+    ASSERT_NOEXCEPT(std::declval<day>() - std::declval<days>());
+    ASSERT_NOEXCEPT(std::declval<day>() - std::declval<day>());
+
+    ASSERT_SAME_TYPE(day,  decltype(std::declval<day>() - std::declval<days>()));
+    ASSERT_SAME_TYPE(days, decltype(std::declval<day>() - std::declval<day>()));
+    
+    static_assert(testConstexpr<day, days>(), "");
+
+    day dy{12};
+    for (unsigned i = 0; i <= 10; ++i)
+    {
+        day d1   = dy - days{i};
+        days off = dy - day {i};
+        assert(static_cast<unsigned>(d1) == 12 - i);
+        assert(off.count() == static_cast<int>(12 - i)); // days is signed
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/plus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/plus.pass.cpp
new file mode 100644
index 000000000..fb8f53612
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/plus.pass.cpp
@@ -0,0 +1,59 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class day;
+
+// constexpr day operator+(const day& x, const days& y) noexcept;
+//   Returns: day(unsigned{x} + y.count()).
+//
+// constexpr day operator+(const days& x, const day& y) noexcept;
+//   Returns: y + x.
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr()
+{
+    D d{1};
+    Ds offset{23};
+    if (d + offset != D{24}) return false;
+    if (offset + d != D{24}) return false;
+    return true;
+}
+
+int main()
+{
+    using day  = std::chrono::day;
+    using days = std::chrono::days;
+
+    ASSERT_NOEXCEPT(std::declval<day>() + std::declval<days>());
+    ASSERT_NOEXCEPT(std::declval<days>() + std::declval<day>());
+
+    ASSERT_SAME_TYPE(day, decltype(std::declval<day>() + std::declval<days>()));
+    ASSERT_SAME_TYPE(day, decltype(std::declval<days>() + std::declval<day>()));
+    
+    static_assert(testConstexpr<day, days>(), "");
+
+    day dy{12};
+    for (unsigned i = 0; i <= 10; ++i)
+    {
+        day d1 = dy + days{i};
+        day d2 = days{i} + dy;
+        assert(d1 == d2);
+        assert(static_cast<unsigned>(d1) == i + 12);
+        assert(static_cast<unsigned>(d2) == i + 12);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..3e859af17
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/time.cal.day.nonmembers/streaming.pass.cpp
@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class day;
+
+// template<class charT, class traits>
+//   basic_ostream<charT, traits>&
+//   operator<<(basic_ostream<charT, traits>& os, const day& d);
+// 
+//   Effects: Inserts format(fmt, d) where fmt is "%d" widened to charT. 
+//                If !d.ok(), appends with " is not a valid day".
+// 
+// template<class charT, class traits>
+//   basic_ostream<charT, traits>&
+//   to_stream(basic_ostream<charT, traits>& os, const charT* fmt, const day& d);
+// 
+//   Effects: Streams d into os using the format specified by the NTCTS fmt. 
+//              fmt encoding follows the rules specified in 25.11.
+// 
+// template<class charT, class traits, class Alloc = allocator<charT>>
+//   basic_istream<charT, traits>&
+//   from_stream(basic_istream<charT, traits>& is, const charT* fmt,
+//             day& d, basic_string<charT, traits, Alloc>* abbrev = nullptr,
+//             minutes* offset = nullptr);
+// 
+//   Effects: Attempts to parse the input stream is into the day d using the format flags
+//             given in the NTCTS fmt as specified in 25.12. 
+//             If the parse fails to decode a valid day, is.setstate(ios_base::failbit)
+//             shall be called and d shall not be modified. 
+//             If %Z is used and successfully parsed, that value will be assigned to *abbrev
+//             if abbrev is non-null. If %z (or a modified variant) is used and
+//             successfully parsed, that value will be assigned to *offset if offset is non-null.
+// 
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+   using day = std::chrono::day;
+   std::cout << day{1};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.day/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.day/types.pass.cpp
new file mode 100644
index 000000000..37c9c570f
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.day/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class day;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using day = std::chrono::day;
+    
+    static_assert(std::is_trivially_copyable_v<day>, "");
+    static_assert(std::is_standard_layout_v<day>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.last/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.last/types.pass.cpp
new file mode 100644
index 000000000..f0d3e3cd2
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.last/types.pass.cpp
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// struct last_spec {
+//   explicit last_spec() = default;
+// };
+//
+// inline constexpr last_spec last{};
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using last_spec = std::chrono::last_spec;
+    
+    ASSERT_SAME_TYPE(const last_spec, decltype(std::chrono::last));
+
+    static_assert(std::is_trivially_copyable_v<last_spec>, "");
+    static_assert(std::is_standard_layout_v<last_spec>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/ctor.pass.cpp
new file mode 100644
index 000000000..2a30bece3
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/ctor.pass.cpp
@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day;
+
+//                     month_day() = default;
+//  constexpr month_day(const chrono::month& m, const chrono::day& d) noexcept;
+//
+//  Effects:  Constructs an object of type month_day by initializing m_ with m, and d_ with d.
+//
+//  constexpr chrono::month month() const noexcept;
+//  constexpr chrono::day     day() const noexcept;
+//  constexpr bool             ok() const noexcept;
+         
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using day       = std::chrono::day;
+    using month     = std::chrono::month;
+    using month_day = std::chrono::month_day;
+
+    ASSERT_NOEXCEPT(month_day{});
+    ASSERT_NOEXCEPT(month_day{month{1}, day{1}});
+    
+    constexpr month_day md0{};
+    static_assert( md0.month() == month{}, "");
+    static_assert( md0.day()   == day{},   "");
+    static_assert(!md0.ok(),               "");
+
+    constexpr month_day md1{std::chrono::January, day{4}};
+    static_assert( md1.month() == std::chrono::January, "");
+    static_assert( md1.day()   == day{4},               "");
+    static_assert( md1.ok(),                            "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/day.pass.cpp b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/day.pass.cpp
new file mode 100644
index 000000000..69477a459
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/day.pass.cpp
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day;
+
+// constexpr chrono::day day() const noexcept;
+//  Returns: d_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using day       = std::chrono::day;
+    using month     = std::chrono::month;
+    using month_day = std::chrono::month_day;
+
+    ASSERT_NOEXCEPT(               std::declval<const month_day>().day());
+    ASSERT_SAME_TYPE(day, decltype(std::declval<const month_day>().day()));
+
+    static_assert( month_day{}.day() == day{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        month_day md(std::chrono::March, day{i});
+        assert( static_cast<unsigned>(md.day()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/month.pass.cpp
new file mode 100644
index 000000000..73ddb6416
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/month.pass.cpp
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day;
+
+// constexpr chrono::month month() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using day       = std::chrono::day;
+    using month     = std::chrono::month;
+    using month_day = std::chrono::month_day;
+
+    ASSERT_NOEXCEPT(                 std::declval<const month_day>().month());
+    ASSERT_SAME_TYPE(month, decltype(std::declval<const month_day>().month()));
+
+    static_assert( month_day{}.month() == month{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        month_day md(month{i}, day{1});
+        assert( static_cast<unsigned>(md.month()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/ok.pass.cpp
new file mode 100644
index 000000000..6ee79caa1
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.members/ok.pass.cpp
@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day;
+
+// constexpr bool ok() const noexcept;
+//  Returns: true if m_.ok() is true, 1d <= d_, and d_ is less than or equal to the
+//    number of days in month m_; otherwise returns false. 
+//  When m_ == February, the number of days is considered to be 29.
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using day       = std::chrono::day;
+    using month     = std::chrono::month;
+    using month_day = std::chrono::month_day;
+
+    ASSERT_NOEXCEPT(                std::declval<const month_day>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const month_day>().ok()));
+
+    static_assert(!month_day{}.ok(),                         "");
+    static_assert( month_day{std::chrono::May, day{2}}.ok(), "");
+
+    assert(!(month_day(std::chrono::April, day{0}).ok()));
+
+    assert( (month_day{std::chrono::March, day{1}}.ok()));
+    for (unsigned i = 1; i <= 12; ++i)
+    {
+        const bool is31 = i == 1 || i == 3 || i == 5 || i == 7 || i == 8 || i == 10 || i == 12;
+        assert(!(month_day{month{i}, day{ 0}}.ok()));
+        assert( (month_day{month{i}, day{ 1}}.ok()));
+        assert( (month_day{month{i}, day{10}}.ok()));
+        assert( (month_day{month{i}, day{29}}.ok()));
+        assert( (month_day{month{i}, day{30}}.ok()) == (i != 2));
+        assert( (month_day{month{i}, day{31}}.ok()) == is31);
+        assert(!(month_day{month{i}, day{32}}.ok()));
+    }
+
+//  If the month is not ok, all the days are bad
+    for (unsigned i = 1; i <= 35; ++i)
+        assert(!(month_day{month{13}, day{i}}.ok()));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..4a5a6c9cb
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day;
+
+// constexpr bool operator==(const month_day& x, const month_day& y) noexcept;
+//   Returns: x.month() == y.month() && x.day() == y.day().
+//
+// constexpr bool operator< (const month_day& x, const month_day& y) noexcept;
+//   Returns: 
+//      If x.month() < y.month() returns true. 
+//      Otherwise, if x.month() > y.month() returns false. 
+//      Otherwise, returns x.day() < y.day().
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using day       = std::chrono::day;
+    using month     = std::chrono::month;
+    using month_day = std::chrono::month_day;
+
+    AssertComparisons6AreNoexcept<month_day>();
+    AssertComparisons6ReturnBool<month_day>();
+    
+    static_assert( testComparisons6(
+        month_day{std::chrono::January, day{1}}, 
+        month_day{std::chrono::January, day{1}},
+        true, false), "");
+    
+    static_assert( testComparisons6(
+        month_day{std::chrono::January, day{1}}, 
+        month_day{std::chrono::January, day{2}},
+        false, true), "");
+
+    static_assert( testComparisons6(
+        month_day{std::chrono::January,  day{1}}, 
+        month_day{std::chrono::February, day{1}},
+        false, true), "");
+
+//  same day, different months
+    for (unsigned i = 1; i < 12; ++i)
+        for (unsigned j = 1; j < 12; ++j)
+            assert((testComparisons6(
+                month_day{month{i}, day{1}}, 
+                month_day{month{j}, day{1}}, 
+                i == j, i < j )));
+    
+//  same month, different days
+    for (unsigned i = 1; i < 31; ++i)
+        for (unsigned j = 1; j < 31; ++j)
+            assert((testComparisons6(
+                month_day{month{2}, day{i}}, 
+                month_day{month{2}, day{j}}, 
+                i == j, i < j )));
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..a197a3e1e
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.md/time.cal.md.nonmembers/streaming.pass.cpp
@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class month_day;
+
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const month_day& md);
+// 
+//     Returns: os << md.month() << '/' << md.day().
+// 
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     to_stream(basic_ostream<charT, traits>& os, const charT* fmt, const month_day& md);
+// 
+// Effects: Streams md into os using the format specified by the NTCTS fmt. 
+//          fmt encoding follows the rules specified in 25.11.
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+#include "test_macros.h"
+
+int main()
+{
+    using month_day = std::chrono::month_day;
+    using month     = std::chrono::month;
+    using day       = std::chrono::day;
+    std::cout << month_day{month{1}, day{1}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.md/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.md/types.pass.cpp
new file mode 100644
index 000000000..2a85c79fe
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.md/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_day = std::chrono::month_day;
+    
+    static_assert(std::is_trivially_copyable_v<month_day>, "");
+    static_assert(std::is_standard_layout_v<month_day>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mdlast/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mdlast/comparisons.pass.cpp
new file mode 100644
index 000000000..f8c74bbd0
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mdlast/comparisons.pass.cpp
@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day_last;
+
+// constexpr bool operator==(const month_day& x, const month_day& y) noexcept;
+//   Returns: x.month() == y.month()
+//
+// constexpr bool operator< (const month_day& x, const month_day& y) noexcept;
+//   Returns: x.month() < y.month()
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using month          = std::chrono::month;
+    using month_day_last = std::chrono::month_day_last;
+
+    AssertComparisons6AreNoexcept<month_day_last>();
+    AssertComparisons6ReturnBool<month_day_last>();
+    
+    static_assert( testComparisons6Values<month_day_last>(month{1}, month{1}), "");
+    static_assert( testComparisons6Values<month_day_last>(month{1}, month{2}), "");
+
+//  same day, different months
+    for (unsigned i = 1; i < 12; ++i)
+        for (unsigned j = 1; j < 12; ++j)
+            assert((testComparisons6Values<month_day_last>(month{i}, month{j})));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mdlast/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mdlast/ctor.pass.cpp
new file mode 100644
index 000000000..3a16ca4d9
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mdlast/ctor.pass.cpp
@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day_last;
+
+//  constexpr month_day_last(const chrono::month& m) noexcept;
+//
+//  Effects:  Constructs an object of type month_day_last by initializing m_ with m
+//
+//  constexpr chrono::month month() const noexcept;
+//  constexpr bool             ok() const noexcept;
+         
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month     = std::chrono::month;
+    using month_day_last = std::chrono::month_day_last;
+
+    ASSERT_NOEXCEPT(month_day_last{month{1}});
+    
+    constexpr month_day_last md0{month{}};
+    static_assert( md0.month() == month{}, "");
+    static_assert(!md0.ok(),               "");
+
+    constexpr month_day_last md1{std::chrono::January};
+    static_assert( md1.month() == std::chrono::January, "");
+    static_assert( md1.ok(),                            "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mdlast/month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mdlast/month.pass.cpp
new file mode 100644
index 000000000..b81d799c2
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mdlast/month.pass.cpp
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day_last;
+
+// constexpr chrono::month month() const noexcept;
+//  Returns: m_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month     = std::chrono::month;
+    using month_day_last = std::chrono::month_day_last;
+
+    ASSERT_NOEXCEPT(                 std::declval<const month_day_last>().month());
+    ASSERT_SAME_TYPE(month, decltype(std::declval<const month_day_last>().month()));
+
+    static_assert( month_day_last{month{}}.month() == month{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        month_day_last mdl(month{i});
+        assert( static_cast<unsigned>(mdl.month()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mdlast/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mdlast/ok.pass.cpp
new file mode 100644
index 000000000..8d97eb601
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mdlast/ok.pass.cpp
@@ -0,0 +1,46 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day_last;
+
+// constexpr bool ok() const noexcept;
+//  Returns: m_.ok()
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month          = std::chrono::month;
+    using month_day_last = std::chrono::month_day_last;
+
+    ASSERT_NOEXCEPT(                std::declval<const month_day_last>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const month_day_last>().ok()));
+
+    static_assert(!month_day_last{month{}}.ok(),          "");
+    static_assert( month_day_last{std::chrono::May}.ok(), "");
+
+    for (unsigned i = 1; i <= 12; ++i)
+    {
+        month_day_last mdl{month{i}};
+        assert( mdl.ok());
+    }
+
+//  If the month is not ok, all the days are bad
+    for (unsigned i = 13; i <= 50; ++i)
+    {
+        month_day_last mdl{month{i}};
+        assert(!mdl.ok());
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mdlast/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mdlast/streaming.pass.cpp
new file mode 100644
index 000000000..693acd89e
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mdlast/streaming.pass.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class month_day_last;
+//
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const month_day_last& mdl);
+// 
+//     Returns: os << mdl.month() << "/last".
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_day_last = std::chrono::month_day_last;
+    using month          = std::chrono::month;
+    std::cout << month_day_last{month{1}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mdlast/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mdlast/types.pass.cpp
new file mode 100644
index 000000000..f50d22aff
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mdlast/types.pass.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// class month_day_last;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_day_last = std::chrono::month_day_last;
+    
+    static_assert(std::is_trivially_copyable_v<month_day_last>, "");
+    static_assert(std::is_standard_layout_v<month_day_last>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/ctor.pass.cpp
new file mode 100644
index 000000000..e9a7abce3
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/ctor.pass.cpp
@@ -0,0 +1,46 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month;
+
+//                     month() = default;
+//  explicit constexpr month(int m) noexcept;
+//  explicit constexpr operator int() const noexcept;
+
+//  Effects: Constructs an object of type month by initializing m_ with m.
+//    The value held is unspecified if d is not in the range [0, 255].
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month = std::chrono::month;
+
+    ASSERT_NOEXCEPT(month{});
+    ASSERT_NOEXCEPT(month(1));
+    ASSERT_NOEXCEPT(static_cast<unsigned>(month(1)));
+    
+    constexpr month m0{};
+    static_assert(static_cast<unsigned>(m0) == 0, "");
+
+    constexpr month m1{1};
+    static_assert(static_cast<unsigned>(m1) == 1, "");
+    
+    for (unsigned i = 0; i <= 255; ++i)
+    {
+        month m(i);
+        assert(static_cast<unsigned>(m) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/decrement.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/decrement.pass.cpp
new file mode 100644
index 000000000..bc39bbc31
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/decrement.pass.cpp
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month;
+
+//  constexpr month& operator--() noexcept;
+//  constexpr month operator--(int) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename M>
+constexpr bool testConstexpr()
+{
+    M m1{10};
+    if (static_cast<unsigned>(--m1) != 9) return false;
+    if (static_cast<unsigned>(m1--) != 9) return false;
+    if (static_cast<unsigned>(m1)   != 8) return false;
+    return true;
+}
+
+int main()
+{
+    using month = std::chrono::month;
+    
+    ASSERT_NOEXCEPT(--(std::declval<month&>())  );
+    ASSERT_NOEXCEPT(  (std::declval<month&>())--);
+
+    ASSERT_SAME_TYPE(month , decltype(  std::declval<month&>()--));
+    ASSERT_SAME_TYPE(month&, decltype(--std::declval<month&>()  ));
+    
+    static_assert(testConstexpr<month>(), "");
+
+    for (unsigned i = 10; i <= 20; ++i)
+    {
+        month month(i);
+        assert(static_cast<unsigned>(--month) == i - 1);
+        assert(static_cast<unsigned>(month--) == i - 1);
+        assert(static_cast<unsigned>(month)   == i - 2);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/increment.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/increment.pass.cpp
new file mode 100644
index 000000000..bdedd6e65
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/increment.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month;
+
+//  constexpr month& operator++() noexcept;
+//  constexpr month operator++(int) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename M>
+constexpr bool testConstexpr()
+{
+    M m1{1};
+    if (static_cast<unsigned>(++m1) != 2) return false;
+    if (static_cast<unsigned>(m1++) != 2) return false;
+    if (static_cast<unsigned>(m1)   != 3) return false;
+    return true;
+}
+
+int main()
+{
+    using month = std::chrono::month;
+    ASSERT_NOEXCEPT(++(std::declval<month&>())  );
+    ASSERT_NOEXCEPT(  (std::declval<month&>())++);
+
+    ASSERT_SAME_TYPE(month , decltype(  std::declval<month&>()++));
+    ASSERT_SAME_TYPE(month&, decltype(++std::declval<month&>()  ));
+    
+    static_assert(testConstexpr<month>(), "");
+
+    for (unsigned i = 0; i <= 10; ++i)
+    {
+        month month(i);
+        assert(static_cast<unsigned>(++month) == i + 1);
+        assert(static_cast<unsigned>(month++) == i + 1);
+        assert(static_cast<unsigned>(month)   == i + 2);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/ok.pass.cpp
new file mode 100644
index 000000000..3bf8f67f6
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/ok.pass.cpp
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month;
+
+// constexpr bool ok() const noexcept;
+//  Returns: 1 <= d_ && d_ <= 12
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month = std::chrono::month;
+
+    ASSERT_NOEXCEPT(                std::declval<const month>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const month>().ok()));
+
+    static_assert(!month{0}.ok(), "");
+    static_assert( month{1}.ok(), "");
+
+    assert(!month{0}.ok());
+    for (unsigned i = 1; i <= 12; ++i)
+        assert(month{i}.ok());
+    for (unsigned i = 13; i <= 255; ++i)
+        assert(!month{i}.ok());
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/plus_minus_equal.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/plus_minus_equal.pass.cpp
new file mode 100644
index 000000000..84d6e9c68
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.members/plus_minus_equal.pass.cpp
@@ -0,0 +1,67 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month;
+
+// constexpr month& operator+=(const month& d) noexcept;
+// constexpr month& operator-=(const month& d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename M, typename Ms>
+constexpr bool testConstexpr()
+{
+    M m1{1};
+    if (static_cast<unsigned>(m1 += Ms{ 1}) !=  2) return false;
+    if (static_cast<unsigned>(m1 += Ms{ 2}) !=  4) return false;
+    if (static_cast<unsigned>(m1 += Ms{ 8}) != 12) return false;
+    if (static_cast<unsigned>(m1 -= Ms{ 1}) != 11) return false;
+    if (static_cast<unsigned>(m1 -= Ms{ 2}) !=  9) return false;
+    if (static_cast<unsigned>(m1 -= Ms{ 8}) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using month  = std::chrono::month;
+    using months = std::chrono::months;
+
+    ASSERT_NOEXCEPT(std::declval<month&>() += std::declval<months&>());
+    ASSERT_NOEXCEPT(std::declval<month&>() -= std::declval<months&>());
+    ASSERT_SAME_TYPE(month&, decltype(std::declval<month&>() += std::declval<months&>()));
+    ASSERT_SAME_TYPE(month&, decltype(std::declval<month&>() -= std::declval<months&>()));
+    
+    static_assert(testConstexpr<month, months>(), "");
+
+    for (unsigned i = 1; i <= 10; ++i)
+    {
+        month month(i);
+        int exp = i + 10;
+        while (exp > 12)
+            exp -= 12;
+        assert(static_cast<unsigned>(month += months{10}) == static_cast<unsigned>(exp));
+        assert(static_cast<unsigned>(month)               == static_cast<unsigned>(exp));
+    }
+
+    for (unsigned i = 1; i <= 10; ++i)
+    {
+        month month(i);
+        int exp = i - 9;
+        while (exp < 1)
+            exp += 12;
+        assert(static_cast<unsigned>(month -= months{ 9}) == static_cast<unsigned>(exp));
+        assert(static_cast<unsigned>(month)               == static_cast<unsigned>(exp));
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..59c45d9dd
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month;
+
+// constexpr bool operator==(const month& x, const month& y) noexcept;
+// constexpr bool operator!=(const month& x, const month& y) noexcept;
+// constexpr bool operator< (const month& x, const month& y) noexcept;
+// constexpr bool operator> (const month& x, const month& y) noexcept;
+// constexpr bool operator<=(const month& x, const month& y) noexcept;
+// constexpr bool operator>=(const month& x, const month& y) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+
+int main()
+{
+    using month = std::chrono::month;
+
+    AssertComparisons6AreNoexcept<month>();
+    AssertComparisons6ReturnBool<month>();
+
+    static_assert(testComparisons6Values<month>(0U ,0U), "");
+    static_assert(testComparisons6Values<month>(0U, 1U), "");
+    
+//  Some 'ok' values as well
+    static_assert(testComparisons6Values<month>( 5U,  5U), "");
+    static_assert(testComparisons6Values<month>( 5U, 10U), "");
+    
+    for (unsigned i = 1; i < 10; ++i)
+        for (unsigned j = 10; j < 10; ++j)
+            assert(testComparisons6Values<month>(i, j));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/literals.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/literals.pass.cpp
new file mode 100644
index 000000000..e17852b58
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/literals.pass.cpp
@@ -0,0 +1,87 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// inline constexpr month January{1};
+// inline constexpr month February{2};
+// inline constexpr month March{3};
+// inline constexpr month April{4};
+// inline constexpr month May{5};
+// inline constexpr month June{6};
+// inline constexpr month July{7};
+// inline constexpr month August{8};
+// inline constexpr month September{9};
+// inline constexpr month October{10};
+// inline constexpr month November{11};
+// inline constexpr month December{12};
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::January));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::February));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::March));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::April));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::May));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::June));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::July));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::August));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::September));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::October));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::November));
+    ASSERT_SAME_TYPE(const std::chrono::month, decltype(std::chrono::December));
+
+    static_assert( std::chrono::January   == std::chrono::month(1),  "");
+    static_assert( std::chrono::February  == std::chrono::month(2),  "");
+    static_assert( std::chrono::March     == std::chrono::month(3),  "");
+    static_assert( std::chrono::April     == std::chrono::month(4),  "");
+    static_assert( std::chrono::May       == std::chrono::month(5),  "");
+    static_assert( std::chrono::June      == std::chrono::month(6),  "");
+    static_assert( std::chrono::July      == std::chrono::month(7),  "");
+    static_assert( std::chrono::August    == std::chrono::month(8),  "");
+    static_assert( std::chrono::September == std::chrono::month(9),  "");
+    static_assert( std::chrono::October   == std::chrono::month(10), "");
+    static_assert( std::chrono::November  == std::chrono::month(11), "");
+    static_assert( std::chrono::December  == std::chrono::month(12), "");
+
+    assert(std::chrono::January   == std::chrono::month(1));
+    assert(std::chrono::February  == std::chrono::month(2));
+    assert(std::chrono::March     == std::chrono::month(3));
+    assert(std::chrono::April     == std::chrono::month(4));
+    assert(std::chrono::May       == std::chrono::month(5));
+    assert(std::chrono::June      == std::chrono::month(6));
+    assert(std::chrono::July      == std::chrono::month(7));
+    assert(std::chrono::August    == std::chrono::month(8));
+    assert(std::chrono::September == std::chrono::month(9));
+    assert(std::chrono::October   == std::chrono::month(10));
+    assert(std::chrono::November  == std::chrono::month(11));
+    assert(std::chrono::December  == std::chrono::month(12));
+
+    assert(static_cast<unsigned>(std::chrono::January)   ==  1);
+    assert(static_cast<unsigned>(std::chrono::February)  ==  2);
+    assert(static_cast<unsigned>(std::chrono::March)     ==  3);
+    assert(static_cast<unsigned>(std::chrono::April)     ==  4);
+    assert(static_cast<unsigned>(std::chrono::May)       ==  5);
+    assert(static_cast<unsigned>(std::chrono::June)      ==  6);
+    assert(static_cast<unsigned>(std::chrono::July)      ==  7);
+    assert(static_cast<unsigned>(std::chrono::August)    ==  8);
+    assert(static_cast<unsigned>(std::chrono::September) ==  9);
+    assert(static_cast<unsigned>(std::chrono::October)   == 10);
+    assert(static_cast<unsigned>(std::chrono::November)  == 11);
+    assert(static_cast<unsigned>(std::chrono::December)  == 12);
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/minus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/minus.pass.cpp
new file mode 100644
index 000000000..055a28755
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/minus.pass.cpp
@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month;
+
+// constexpr month operator-(const month& x, const months& y) noexcept;
+//   Returns: x + -y.
+//
+// constexpr months operator-(const month& x, const month& y) noexcept;
+//   Returns: If x.ok() == true and y.ok() == true, returns a value m in the range 
+//   [months{0}, months{11}] satisfying y + m == x. 
+//   Otherwise the value returned is unspecified. 
+//   [Example: January - February == months{11}. —end example]
+
+extern "C" int printf(const char *, ...);
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename M, typename Ms>
+constexpr bool testConstexpr()
+{
+    {
+    M m{5};
+    Ms offset{3};
+    if (m - offset != M{2}) return false;
+    if (m - M{2} != offset) return false;
+    }
+
+//  Check the example
+    if (M{1} - M{2} != Ms{11}) return false;
+    return true;
+}
+
+#include <iostream>
+
+int main()
+{
+    using month  = std::chrono::month;
+    using months = std::chrono::months;
+
+    ASSERT_NOEXCEPT(std::declval<month>() - std::declval<months>());
+    ASSERT_NOEXCEPT(std::declval<month>() - std::declval<month>());
+
+    ASSERT_SAME_TYPE(month , decltype(std::declval<month>() - std::declval<months>()));
+    ASSERT_SAME_TYPE(months, decltype(std::declval<month>() - std::declval<month> ()));
+    
+static_assert(testConstexpr<month, months>(), "");
+
+    month m{6};
+    for (unsigned i = 1; i <= 12; ++i)
+    {
+        month m1   = m - months{i};
+//      months off = m - month {i};
+        int exp = 6 - i;
+        if (exp < 1)
+            exp += 12;
+        assert(static_cast<unsigned>(m1) == static_cast<unsigned>(exp));
+//          assert(off.count()               == static_cast<unsigned>(exp));
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/plus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/plus.pass.cpp
new file mode 100644
index 000000000..31fc277cb
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/plus.pass.cpp
@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month;
+
+// constexpr month operator+(const month& x, const months& y) noexcept;
+//   Returns: month(int{x} + y.count()).
+//
+// constexpr month operator+(const months& x, const month& y) noexcept;
+//   Returns:
+//     month{modulo(static_cast<long long>(int{x}) + (y.count() - 1), 12) + 1}
+//   where modulo(n, 12) computes the remainder of n divided by 12 using Euclidean division. 
+//   [Note: Given a divisor of 12, Euclidean division truncates towards negative infinity
+//   and always produces a remainder in the range of [0, 11]. 
+//   Assuming no overflow in the signed summation, this operation results in a month
+//   holding a value in the range [1, 12] even if !x.ok(). —end note]
+//   [Example: February + months{11} == January. —end example]
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename M, typename Ms>
+constexpr bool testConstexpr()
+{
+    M m{1};
+    Ms offset{4};
+    if (m + offset != M{5}) return false;
+    if (offset + m != M{5}) return false;
+//  Check the example
+    if (M{2} + Ms{11} != M{1}) return false;
+    return true;
+}
+
+int main()
+{
+    using month  = std::chrono::month;
+    using months = std::chrono::months;
+
+    ASSERT_NOEXCEPT(std::declval<month>() + std::declval<months>());
+    ASSERT_NOEXCEPT(std::declval<months>() + std::declval<month>());
+
+    ASSERT_SAME_TYPE(month, decltype(std::declval<month>()  + std::declval<months>()));
+    ASSERT_SAME_TYPE(month, decltype(std::declval<months>() + std::declval<month>() ));
+    
+    static_assert(testConstexpr<month, months>(), "");
+
+    month my{2};
+    for (unsigned i = 0; i <= 15; ++i)
+    {
+        month m1 = my + months{i};
+        month m2 = months{i} + my;
+        assert(m1 == m2);
+        unsigned exp = i + 2;
+        while (exp > 12)
+            exp -= 12;
+        assert(static_cast<unsigned>(m1) == exp);
+        assert(static_cast<unsigned>(m2) == exp);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..274360de4
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/time.cal.month.nonmembers/streaming.pass.cpp
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class month;
+
+// template<class charT, class traits>
+//   basic_ostream<charT, traits>&
+//   operator<<(basic_ostream<charT, traits>& os, const month& m);
+// 
+//   Effects: If m.ok() == true inserts format(os.getloc(), fmt, m) where fmt is "%b" widened to charT. 
+//   Otherwise inserts int{m} << " is not a valid month".
+// 
+// template<class charT, class traits>
+//   basic_ostream<charT, traits>&
+//   to_stream(basic_ostream<charT, traits>& os, const charT* fmt, const month& m);
+// 
+//   Effects: Streams m into os using the format specified by the NTCTS fmt. 
+//   fmt encoding follows the rules specified in 25.11.
+// 
+// template<class charT, class traits, class Alloc = allocator<charT>>
+//   basic_istream<charT, traits>&
+//   from_stream(basic_istream<charT, traits>& is, const charT* fmt,
+//             month& m, basic_string<charT, traits, Alloc>* abbrev = nullptr,
+//             minutes* offset = nullptr);
+// 
+//   Effects: Attempts to parse the input stream is into the month m using the format flags 
+//   given in the NTCTS fmt as specified in 25.12. If the parse fails to decode a valid month,
+//   is.setstate(ios_- base::failbit) shall be called and m shall not be modified. 
+//   If %Z is used and successfully parsed, that value will be assigned to *abbrev if 
+//   abbrev is non-null. If %z (or a modified variant) is used and successfully parsed, 
+//   that value will be assigned to *offset if offset is non-null.
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+   using month = std::chrono::month;
+   std::cout << month{1};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.month/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.month/types.pass.cpp
new file mode 100644
index 000000000..e0dc20e11
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.month/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month = std::chrono::month;
+    
+    static_assert(std::is_trivially_copyable_v<month>, "");
+    static_assert(std::is_standard_layout_v<month>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/ctor.pass.cpp
new file mode 100644
index 000000000..9b952c4ad
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/ctor.pass.cpp
@@ -0,0 +1,46 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday;
+//   month_weekday represents the nth weekday of a month, of an as yet unspecified year.
+
+//  constexpr month_weekday(const chrono::month& m, const chrono::weekday_indexed& wdi) noexcept;
+//    Effects:  Constructs an object of type month_weekday by initializing m_ with m, and wdi_ with wdi.
+//
+//  constexpr chrono::month                     month() const noexcept;
+//  constexpr chrono::weekday_indexed weekday_indexed() const noexcept;
+//  constexpr bool                                 ok() const noexcept;
+         
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_weekday   = std::chrono::month_weekday;
+    using month           = std::chrono::month;
+    using weekday         = std::chrono::weekday;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    ASSERT_NOEXCEPT(month_weekday{month{1}, weekday_indexed{weekday{}, 1}});
+    
+    constexpr month_weekday md0{month{}, weekday_indexed{}};
+    static_assert( md0.month()           == month{},           "");
+    static_assert( md0.weekday_indexed() == weekday_indexed{}, "");
+    static_assert(!md0.ok(),                                   "");
+
+    constexpr month_weekday md1{std::chrono::January, weekday_indexed{std::chrono::Friday, 4}};
+    static_assert( md1.month() == std::chrono::January,                              "");
+    static_assert( md1.weekday_indexed() == weekday_indexed{std::chrono::Friday, 4}, "");
+    static_assert( md1.ok(),                                                         "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/month.pass.cpp
new file mode 100644
index 000000000..21d2748f6
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/month.pass.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday;
+
+// constexpr chrono::month month() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_weekday   = std::chrono::month_weekday;
+    using month           = std::chrono::month;
+    using weekday         = std::chrono::weekday;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    constexpr weekday Sunday = std::chrono::Sunday;
+
+    ASSERT_NOEXCEPT(                 std::declval<const month_weekday>().month());
+    ASSERT_SAME_TYPE(month, decltype(std::declval<const month_weekday>().month()));
+
+    static_assert( month_weekday{}.month() == month{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        month_weekday md(month{i}, weekday_indexed{Sunday, 1});
+        assert( static_cast<unsigned>(md.month()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/ok.pass.cpp
new file mode 100644
index 000000000..bb1bd3566
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/ok.pass.cpp
@@ -0,0 +1,51 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday;
+
+// constexpr bool ok() const noexcept;
+//  Returns: m_.ok() && wdi_.ok().
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_weekday   = std::chrono::month_weekday;
+    using month           = std::chrono::month;
+    using weekday         = std::chrono::weekday;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    constexpr weekday Sunday = std::chrono::Sunday;
+
+    ASSERT_NOEXCEPT(                std::declval<const month_weekday>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const month_weekday>().ok()));
+
+    static_assert(!month_weekday{month{}, weekday_indexed{}}.ok(),                   "");
+    static_assert( month_weekday{std::chrono::May, weekday_indexed{Sunday, 2}}.ok(), "");
+
+    assert(!(month_weekday(std::chrono::April, weekday_indexed{Sunday, 0}).ok()));
+    assert( (month_weekday{std::chrono::March, weekday_indexed{Sunday, 1}}.ok()));
+
+    for (unsigned i = 1; i <= 12; ++i)
+        for (unsigned j = 0; j <= 6; ++j)
+        {
+            month_weekday mwd{month{i}, weekday_indexed{Sunday, j}};
+            assert(mwd.ok() == (j >= 1 && j <= 5));
+        }
+
+//  If the month is not ok, all the weekday_indexed are bad
+    for (unsigned i = 1; i <= 10; ++i)
+        assert(!(month_weekday{month{13}, weekday_indexed{Sunday, i}}.ok()));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/weekday_indexed.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/weekday_indexed.pass.cpp
new file mode 100644
index 000000000..9aebab26f
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.members/weekday_indexed.pass.cpp
@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday;
+
+// constexpr chrono::weekday_indexed weekday_indexed() const noexcept;
+//  Returns: wdi_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_weekday   = std::chrono::month_weekday;
+    using month           = std::chrono::month;
+    using weekday         = std::chrono::weekday;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    constexpr weekday Sunday = std::chrono::Sunday;
+
+    ASSERT_NOEXCEPT(                           std::declval<const month_weekday>().weekday_indexed());
+    ASSERT_SAME_TYPE(weekday_indexed, decltype(std::declval<const month_weekday>().weekday_indexed()));
+
+    static_assert( month_weekday{month{}, weekday_indexed{}}.weekday_indexed() == weekday_indexed{}, "");
+
+    for (unsigned i = 1; i <= 10; ++i)
+    {
+        month_weekday md(std::chrono::March, weekday_indexed{Sunday, i});
+        assert( static_cast<unsigned>(md.weekday_indexed().weekday() == Sunday));
+        assert( static_cast<unsigned>(md.weekday_indexed().index() == i));
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..60361382d
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,86 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday;
+
+// constexpr bool operator==(const month_weekday& x, const month_weekday& y) noexcept;
+//   Returns: x.month() == y.month() && x.day() == y.day().
+//
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using month_weekday   = std::chrono::month_weekday;
+    using month           = std::chrono::month;
+    using weekday_indexed = std::chrono::weekday_indexed;
+    using weekday         = std::chrono::weekday;
+
+    constexpr weekday Sunday = std::chrono::Sunday;
+    constexpr weekday Monday = std::chrono::Monday;
+
+    AssertComparisons2AreNoexcept<month_weekday>();
+    AssertComparisons2ReturnBool<month_weekday>();
+    
+    static_assert( testComparisons2(
+        month_weekday{std::chrono::January, weekday_indexed{Sunday, 1}}, 
+        month_weekday{std::chrono::January, weekday_indexed{Sunday, 1}},
+        true), "");
+    
+    static_assert( testComparisons2(
+        month_weekday{std::chrono::January, weekday_indexed{Sunday, 1}},
+        month_weekday{std::chrono::January, weekday_indexed{Sunday, 2}},
+        false), "");
+
+    static_assert( testComparisons2(
+        month_weekday{std::chrono::January,  weekday_indexed{Sunday, 1}},
+        month_weekday{std::chrono::February, weekday_indexed{Sunday, 1}},
+        false), "");
+
+    static_assert( testComparisons2(
+        month_weekday{std::chrono::January, weekday_indexed{Monday, 1}},
+        month_weekday{std::chrono::January, weekday_indexed{Sunday, 2}},
+        false), "");
+
+    static_assert( testComparisons2(
+        month_weekday{std::chrono::January,  weekday_indexed{Monday, 1}},
+        month_weekday{std::chrono::February, weekday_indexed{Sunday, 1}},
+        false), "");
+
+//  same day, different months
+    for (unsigned i = 1; i < 12; ++i)
+        for (unsigned j = 1; j < 12; ++j)
+            assert((testComparisons2(
+                month_weekday{month{i}, weekday_indexed{Sunday, 1}}, 
+                month_weekday{month{j}, weekday_indexed{Sunday, 1}}, 
+                i == j)));
+    
+//  same month, different weeks
+    for (unsigned i = 1; i < 5; ++i)
+        for (unsigned j = 1; j < 5; ++j)
+            assert((testComparisons2(
+                month_weekday{month{2}, weekday_indexed{Sunday, i}}, 
+                month_weekday{month{2}, weekday_indexed{Sunday, j}}, 
+                i == j)));
+
+//  same month, different days
+    for (unsigned i = 0; i < 6; ++i)
+        for (unsigned j = 0; j < 6; ++j)
+            assert((testComparisons2(
+                month_weekday{month{2}, weekday_indexed{weekday{i}, 2}}, 
+                month_weekday{month{2}, weekday_indexed{weekday{j}, 2}}, 
+                i == j)));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..be2e46add
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwd/time.cal.mwd.nonmembers/streaming.pass.cpp
@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class month_weekday;
+
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const month_weekday& mwd);
+// 
+//     Returns: os << mwd.month() << '/' << mwd.weekday_indexed().
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_weekday   = std::chrono::month_weekday;
+    using month           = std::chrono::month;
+    using weekday_indexed = std::chrono::weekday_indexed;
+    using weekday         = std::chrono::weekday;
+    
+    std::cout << month_weekday{month{1}, weekday_indexed{weekday{3}, 3}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwd/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwd/types.pass.cpp
new file mode 100644
index 000000000..2fcf9b0fe
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwd/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_weekday = std::chrono::month_weekday;
+    
+    static_assert(std::is_trivially_copyable_v<month_weekday>, "");
+    static_assert(std::is_standard_layout_v<month_weekday>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/ctor.pass.cpp
new file mode 100644
index 000000000..25cfed69b
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/ctor.pass.cpp
@@ -0,0 +1,60 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday_last;
+
+//  constexpr month_weekday_last(const chrono::month& m,
+//                               const chrono::weekday_last& wdl) noexcept;
+//
+//  Effects:  Constructs an object of type month_weekday_last by
+//            initializing m_ with m, and wdl_ with wdl.
+//
+//     constexpr chrono::month        month() const noexcept;
+//     constexpr chrono::weekday_last weekday_last()  const noexcept;
+//     constexpr bool                 ok()    const noexcept;
+    
+             
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month              = std::chrono::month;
+    using weekday            = std::chrono::weekday;
+    using weekday_last       = std::chrono::weekday_last;
+    using month_weekday_last = std::chrono::month_weekday_last;
+
+    constexpr month January = std::chrono::January;
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+
+    ASSERT_NOEXCEPT(month_weekday_last{January, weekday_last{Tuesday}});
+    
+//  bad month
+    constexpr month_weekday_last mwdl1{month{}, weekday_last{Tuesday}};
+    static_assert( mwdl1.month() == month{},                      "");
+    static_assert( mwdl1.weekday_last() == weekday_last{Tuesday}, "");
+    static_assert(!mwdl1.ok(),                                    "");
+
+//  bad weekday_last
+    constexpr month_weekday_last mwdl2{January, weekday_last{weekday{16}}};
+    static_assert( mwdl2.month() == January,                          "");
+    static_assert( mwdl2.weekday_last() == weekday_last{weekday{16}}, "");
+    static_assert(!mwdl2.ok(),                                        "");
+
+//  Good month and weekday_last
+    constexpr month_weekday_last mwdl3{January, weekday_last{weekday{4}}};
+    static_assert( mwdl3.month() == January,                         "");
+    static_assert( mwdl3.weekday_last() == weekday_last{weekday{4}}, "");
+    static_assert( mwdl3.ok(),                                       "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/month.pass.cpp
new file mode 100644
index 000000000..fb3fa5de1
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/month.pass.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday_last;
+
+// constexpr chrono::month month() const noexcept;
+//  Returns: m_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month              = std::chrono::month;
+    using weekday            = std::chrono::weekday;
+    using weekday_last       = std::chrono::weekday_last;
+    using month_weekday_last = std::chrono::month_weekday_last;
+
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+
+    ASSERT_NOEXCEPT(                 std::declval<const month_weekday_last>().month());
+    ASSERT_SAME_TYPE(month, decltype(std::declval<const month_weekday_last>().month()));
+
+    static_assert( month_weekday_last{month{}, weekday_last{Tuesday}}.month() == month{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        month_weekday_last mdl(month{i}, weekday_last{Tuesday});
+        assert( static_cast<unsigned>(mdl.month()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/ok.pass.cpp
new file mode 100644
index 000000000..c55a0f663
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/ok.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday_last;
+
+// constexpr bool ok() const noexcept;
+//  Returns: m_.ok() && wdl_.ok().
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month              = std::chrono::month;
+    using weekday            = std::chrono::weekday;
+    using weekday_last       = std::chrono::weekday_last;
+    using month_weekday_last = std::chrono::month_weekday_last;
+
+    constexpr month January            = std::chrono::January;
+    constexpr weekday Tuesday          = std::chrono::Tuesday;
+    constexpr weekday_last lastTuesday = weekday_last{Tuesday};
+
+    ASSERT_NOEXCEPT(                std::declval<const month_weekday_last>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const month_weekday_last>().ok()));
+
+    static_assert(!month_weekday_last{month{}, lastTuesday}.ok(),               ""); // Bad month
+    static_assert(!month_weekday_last{January, weekday_last{weekday{12}}}.ok(), ""); // Bad month
+    static_assert( month_weekday_last{January, lastTuesday}.ok(),               ""); // Both OK
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        month_weekday_last mwdl{month{i}, lastTuesday};
+        assert( mwdl.ok() == month{i}.ok());
+    }
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        month_weekday_last mwdl{January, weekday_last{weekday{i}}};
+        assert( mwdl.ok() == weekday_last{weekday{i}}.ok());
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/weekday_last.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/weekday_last.pass.cpp
new file mode 100644
index 000000000..bf3a44c3f
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.members/weekday_last.pass.cpp
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday_last;
+
+// constexpr chrono::weekday_last weekday_last() const noexcept;
+//  Returns: wdl_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month              = std::chrono::month;
+    using weekday            = std::chrono::weekday;
+    using weekday_last       = std::chrono::weekday_last;
+    using month_weekday_last = std::chrono::month_weekday_last;
+
+    constexpr month January            = std::chrono::January;
+    constexpr weekday Tuesday          = std::chrono::Tuesday;
+    constexpr weekday_last lastTuesday = weekday_last{Tuesday};
+
+    ASSERT_NOEXCEPT(                        std::declval<const month_weekday_last>().weekday_last());
+    ASSERT_SAME_TYPE(weekday_last, decltype(std::declval<const month_weekday_last>().weekday_last()));
+
+    static_assert( month_weekday_last{month{}, lastTuesday}.weekday_last() == lastTuesday, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        month_weekday_last mdl(January, weekday_last{weekday{i}});
+        assert( static_cast<unsigned>(mdl.weekday_last().weekday()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..2c4153494
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,73 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday_last;
+
+// constexpr bool operator==(const month_weekday_last& x, const month_weekday_last& y) noexcept;
+//   Returns: x.month() == y.month()
+//
+// constexpr bool operator< (const month_weekday_last& x, const month_weekday_last& y) noexcept;
+//   Returns: x.month() < y.month()
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using month              = std::chrono::month;
+    using weekday_last       = std::chrono::weekday_last;
+    using weekday            = std::chrono::weekday;
+    using month_weekday_last = std::chrono::month_weekday_last;
+
+    constexpr month January = std::chrono::January;
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    constexpr weekday Wednesday = std::chrono::Wednesday;
+
+    AssertComparisons2AreNoexcept<month_weekday_last>();
+    AssertComparisons2ReturnBool<month_weekday_last>();
+
+    static_assert( testComparisons2(
+        month_weekday_last{std::chrono::January, weekday_last{Tuesday}}, 
+        month_weekday_last{std::chrono::January, weekday_last{Tuesday}},
+        true), "");
+
+    static_assert( testComparisons2(
+        month_weekday_last{std::chrono::January, weekday_last{Tuesday}}, 
+        month_weekday_last{std::chrono::January, weekday_last{Wednesday}},
+        false), "");
+
+//  vary the months
+    for (unsigned i = 1; i < 12; ++i)
+        for (unsigned j = 1; j < 12; ++j)
+            assert((testComparisons2(
+                month_weekday_last{month{i}, weekday_last{Tuesday}},
+                month_weekday_last{month{j}, weekday_last{Tuesday}},
+            i == j)));
+
+//  vary the weekday
+    for (unsigned i = 0; i < 6; ++i)
+        for (unsigned j = 0; j < 6; ++j)
+            assert((testComparisons2(
+                month_weekday_last{January, weekday_last{weekday{i}}},
+                month_weekday_last{January, weekday_last{weekday{j}}},
+            i == j)));
+
+//  both different
+        assert((testComparisons2(
+            month_weekday_last{month{1}, weekday_last{weekday{1}}},
+            month_weekday_last{month{2}, weekday_last{weekday{2}}},
+        false)));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..b8c22cc8f
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwdlast/time.cal.mwdlast.nonmembers/streaming.pass.cpp
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class month_weekday_last;
+//
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const month_weekday_last& mdl);
+// 
+//     Returns: os << mdl.month() << "/last".
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_weekday_last = std::chrono::month_weekday_last;
+    using month              = std::chrono::month;
+    using weekday            = std::chrono::weekday;
+    using weekday_last       = std::chrono::weekday_last;
+    
+    std::cout << month_weekday_last{month{1}, weekday_last{weekday{3}}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.mwdlast/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.mwdlast/types.pass.cpp
new file mode 100644
index 000000000..b8ffe35e2
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.mwdlast/types.pass.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// class month_weekday_last;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month_weekday_last = std::chrono::month_weekday_last;
+    
+    static_assert(std::is_trivially_copyable_v<month_weekday_last>, "");
+    static_assert(std::is_standard_layout_v<month_weekday_last>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.operators/month_day.pass.cpp b/test/std/utilities/time/time.cal/time.cal.operators/month_day.pass.cpp
new file mode 100644
index 000000000..679e6c4b8
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.operators/month_day.pass.cpp
@@ -0,0 +1,108 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day;
+
+// constexpr month_day
+//   operator/(const month& m, const day& d) noexcept;
+// Returns: {m, d}.
+// 
+// constexpr month_day
+//   operator/(const day& d, const month& m) noexcept;
+// Returns: m / d.
+
+// constexpr month_day
+//   operator/(const month& m, int d) noexcept;
+// Returns: m / day(d). 
+// 
+// constexpr month_day
+//   operator/(int m, const day& d) noexcept;
+// Returns: month(m) / d.
+// 
+// constexpr month_day
+//   operator/(const day& d, int m) noexcept;
+// Returns: month(m) / d.
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using month_day = std::chrono::month_day;
+    using month     = std::chrono::month;
+    using day       = std::chrono::day;
+
+    constexpr month February = std::chrono::February;
+    
+    { // operator/(const month& m, const day& d) (and switched)
+        ASSERT_NOEXCEPT (                    February/day{1});
+        ASSERT_SAME_TYPE(month_day, decltype(February/day{1}));
+        ASSERT_NOEXCEPT (                    day{1}/February);
+        ASSERT_SAME_TYPE(month_day, decltype(day{1}/February));
+
+        for (int i = 1; i <= 12; ++i)
+            for (unsigned j = 0; j <= 30; ++j)
+            {
+                month m(i);
+                day   d{j};
+                month_day md1 = m/d;
+                month_day md2 = d/m;
+                assert(md1.month() == m);
+                assert(md1.day()   == d);
+                assert(md2.month() == m);
+                assert(md2.day()   == d);
+                assert(md1 == md2);
+            }
+    }
+
+
+    { // operator/(const month& m, int d) (NOT switched)
+        ASSERT_NOEXCEPT (                    February/2);
+        ASSERT_SAME_TYPE(month_day, decltype(February/2));
+
+        for (int i = 1; i <= 12; ++i)
+            for (unsigned j = 0; j <= 30; ++j)
+            {
+                month m(i);
+                day   d(j);
+                month_day md1 = m/j;
+                assert(md1.month() == m);
+                assert(md1.day()   == d);
+            }
+    }
+
+
+    { // operator/(const day& d, int m) (and switched)
+        ASSERT_NOEXCEPT (                    day{2}/2);
+        ASSERT_SAME_TYPE(month_day, decltype(day{2}/2));
+        ASSERT_NOEXCEPT (                    2/day{2});
+        ASSERT_SAME_TYPE(month_day, decltype(2/day{2}));
+
+        for (int i = 1; i <= 12; ++i)
+            for (unsigned j = 0; j <= 30; ++j)
+            {
+                month m(i);
+                day   d(j);
+                month_day md1 = d/i;
+                month_day md2 = i/d;
+                assert(md1.month() == m);
+                assert(md1.day()   == d);
+                assert(md2.month() == m);
+                assert(md2.day()   == d);
+                assert(md1 == md2);
+            }
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.operators/month_day_last.pass.cpp b/test/std/utilities/time/time.cal/time.cal.operators/month_day_last.pass.cpp
new file mode 100644
index 000000000..fdba305c9
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.operators/month_day_last.pass.cpp
@@ -0,0 +1,107 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_day_last;
+
+// constexpr month_day_last
+//   operator/(const month& m, last_spec) noexcept;
+// Returns: month_day_last{m}.
+// 
+// constexpr month_day_last
+//   operator/(int m, last_spec) noexcept;
+// Returns: month(m) / last.
+// 
+// constexpr month_day_last
+//   operator/(last_spec, const month& m) noexcept;
+// Returns: m / last. 
+// 
+// constexpr month_day_last
+//   operator/(last_spec, int m) noexcept;
+// Returns: month(m) / last.
+//
+//
+// [Note: A month_day_last object can be constructed using the expression m/last or last/m,
+//     where m is an expression of type month. — end note]
+// [Example:
+//     constexpr auto mdl = February/last; // mdl is the last day of February of an as yet unspecified year
+//     static_assert(mdl.month() == February);
+// --end example]
+
+
+
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using month          = std::chrono::month;
+    using month_day_last = std::chrono::month_day_last;
+    
+    constexpr month February = std::chrono::February;
+    constexpr std::chrono::last_spec last = std::chrono::last;
+
+    ASSERT_SAME_TYPE(month_day_last, decltype(last/February));
+    ASSERT_SAME_TYPE(month_day_last, decltype(February/last));
+
+//  Run the example
+    {
+    constexpr auto mdl = February/std::chrono::last;
+    static_assert(mdl.month() == February, "");
+    }
+    
+    { // operator/(const month& m, last_spec) and switched
+        ASSERT_NOEXCEPT (                         last/February);
+        ASSERT_SAME_TYPE(month_day_last, decltype(last/February));
+        ASSERT_NOEXCEPT (                         February/last);
+        ASSERT_SAME_TYPE(month_day_last, decltype(February/last));
+
+        static_assert((last/February).month() == February, "");
+        static_assert((February/last).month() == February, "");
+
+        for (unsigned i = 1; i < 12; ++i)
+        {
+            month m{i};
+            month_day_last mdl1 = last/m;
+            month_day_last mdl2 = m/last;
+            assert(mdl1.month() == m);
+            assert(mdl2.month() == m);
+            assert(mdl1 == mdl2);
+        }
+    }
+
+    { // operator/(int, last_spec) and switched
+        ASSERT_NOEXCEPT (                         last/2);
+        ASSERT_SAME_TYPE(month_day_last, decltype(last/2));
+        ASSERT_NOEXCEPT (                         2/last);
+        ASSERT_SAME_TYPE(month_day_last, decltype(2/last));
+
+        static_assert((last/2).month() == February, "");
+        static_assert((2/last).month() == February, "");
+
+        for (unsigned i = 1; i < 12; ++i)
+        {
+            month m{i};
+            month_day_last mdl1 = last/i;
+            month_day_last mdl2 = i/last;
+            assert(mdl1.month() == m);
+            assert(mdl2.month() == m);
+            assert(mdl1 == mdl2);
+        }
+    }
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.operators/month_weekday.pass.cpp b/test/std/utilities/time/time.cal/time.cal.operators/month_weekday.pass.cpp
new file mode 100644
index 000000000..e23dfef84
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.operators/month_weekday.pass.cpp
@@ -0,0 +1,115 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday;
+
+// constexpr month_weekday
+//   operator/(const month& m, const weekday_indexed& wdi) noexcept;
+// Returns: {m, wdi}.
+//
+// constexpr month_weekday
+//   operator/(int m, const weekday_indexed& wdi) noexcept;
+// Returns: month(m) / wdi.
+//
+// constexpr month_weekday
+//   operator/(const weekday_indexed& wdi, const month& m) noexcept;
+// Returns: m / wdi. constexpr month_weekday
+//
+// constexpr month_weekday
+//   operator/(const weekday_indexed& wdi, int m) noexcept;
+// Returns: month(m) / wdi.
+
+
+//
+// [Example:
+// constexpr auto mwd = February/Tuesday[3]; // mwd is the third Tuesday of February of an as yet unspecified year
+//      static_assert(mwd.month() == February);
+//      static_assert(mwd.weekday_indexed() == Tuesday[3]);
+// —end example]
+
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using month_weekday   = std::chrono::month_weekday;
+    using month           = std::chrono::month;
+    using weekday         = std::chrono::weekday;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    constexpr month February = std::chrono::February;
+    
+    { // operator/(const month& m, const weekday_indexed& wdi) (and switched)
+        ASSERT_NOEXCEPT (February/Tuesday[2]);
+        ASSERT_SAME_TYPE(month_weekday, decltype(February/Tuesday[2]));
+        ASSERT_NOEXCEPT (Tuesday[2]/February);
+        ASSERT_SAME_TYPE(month_weekday, decltype(Tuesday[2]/February));
+
+    //  Run the example
+        {
+        constexpr month_weekday wdi = February/Tuesday[3];
+        static_assert(wdi.month()           == February,   "");
+        static_assert(wdi.weekday_indexed() == Tuesday[3], "");
+        }
+    
+        for (int i = 1; i <= 12; ++i)
+            for (unsigned j = 0; j <= 6; ++j)
+                for (unsigned k = 1; k <= 5; ++k)
+                {
+                    month m(i);
+                    weekday_indexed wdi = weekday{j}[k];
+                    month_weekday mwd1 = m/wdi;
+                    month_weekday mwd2 = wdi/m;
+                    assert(mwd1.month() == m);
+                    assert(mwd1.weekday_indexed() == wdi);
+                    assert(mwd2.month() == m);
+                    assert(mwd2.weekday_indexed() == wdi);
+                    assert(mwd1 == mwd2);
+                }
+    } 
+
+
+    { // operator/(int m, const weekday_indexed& wdi) (and switched)
+        ASSERT_NOEXCEPT (2/Tuesday[2]);
+        ASSERT_SAME_TYPE(month_weekday, decltype(2/Tuesday[2]));
+        ASSERT_NOEXCEPT (Tuesday[2]/2);
+        ASSERT_SAME_TYPE(month_weekday, decltype(Tuesday[2]/2));
+
+    //  Run the example
+        {
+        constexpr month_weekday wdi = 2/Tuesday[3];
+        static_assert(wdi.month()           == February,   "");
+        static_assert(wdi.weekday_indexed() == Tuesday[3], "");
+        }
+    
+        for (int i = 1; i <= 12; ++i)
+            for (unsigned j = 0; j <= 6; ++j)
+                for (unsigned k = 1; k <= 5; ++k)
+                {
+                    weekday_indexed wdi = weekday{j}[k];
+                    month_weekday mwd1 = i/wdi;
+                    month_weekday mwd2 = wdi/i;
+                    assert(mwd1.month() == month(i));
+                    assert(mwd1.weekday_indexed() == wdi);
+                    assert(mwd2.month() == month(i));
+                    assert(mwd2.weekday_indexed() == wdi);
+                    assert(mwd1 == mwd2);
+                }
+    } 
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.operators/month_weekday_last.pass.cpp b/test/std/utilities/time/time.cal/time.cal.operators/month_weekday_last.pass.cpp
new file mode 100644
index 000000000..f3a0233cb
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.operators/month_weekday_last.pass.cpp
@@ -0,0 +1,107 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class month_weekday_last;
+
+// constexpr month_weekday_last
+//   operator/(const month& m, const weekday_last& wdl) noexcept;
+// Returns: {m, wdl}.
+// 
+// constexpr month_weekday_last
+//   operator/(int m, const weekday_last& wdl) noexcept;
+// Returns: month(m) / wdl.
+// 
+// constexpr month_weekday_last
+//   operator/(const weekday_last& wdl, const month& m) noexcept;
+// Returns: m / wdl.
+// 
+// constexpr month_weekday_last
+//   operator/(const weekday_last& wdl, int m) noexcept;
+// Returns: month(m) / wdl.
+
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using month_weekday      = std::chrono::month_weekday;
+    using month              = std::chrono::month;
+    using weekday            = std::chrono::weekday;
+    using weekday_last       = std::chrono::weekday_last;
+    using month_weekday_last = std::chrono::month_weekday_last;
+
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    constexpr month February = std::chrono::February;
+    constexpr std::chrono::last_spec last = std::chrono::last;
+    
+    { // operator/(const month& m, const weekday_last& wdi) (and switched)
+        ASSERT_NOEXCEPT (February/Tuesday[last]);
+        ASSERT_SAME_TYPE(month_weekday_last, decltype(February/Tuesday[last]));
+        ASSERT_NOEXCEPT (Tuesday[last]/February);
+        ASSERT_SAME_TYPE(month_weekday_last, decltype(Tuesday[last]/February));
+
+    //  Run the example
+        {
+        constexpr month_weekday_last wdi = February/Tuesday[last];
+        static_assert(wdi.month()        == February,      "");
+        static_assert(wdi.weekday_last() == Tuesday[last], "");
+        }
+    
+        for (int i = 1; i <= 12; ++i)
+            for (unsigned j = 0; j <= 6; ++j)
+            {
+                month m(i);
+                weekday_last wdi = weekday{j}[last];
+                month_weekday_last mwd1 = m/wdi;
+                month_weekday_last mwd2 = wdi/m;
+                assert(mwd1.month() == m);
+                assert(mwd1.weekday_last() == wdi);
+                assert(mwd2.month() == m);
+                assert(mwd2.weekday_last() == wdi);
+                assert(mwd1 == mwd2);
+            }
+    }
+
+
+    { // operator/(int m, const weekday_last& wdi) (and switched)
+        ASSERT_NOEXCEPT (2/Tuesday[2]);
+        ASSERT_SAME_TYPE(month_weekday_last, decltype(2/Tuesday[last]));
+        ASSERT_NOEXCEPT (Tuesday[2]/2);
+        ASSERT_SAME_TYPE(month_weekday_last, decltype(Tuesday[last]/2));
+
+    //  Run the example
+        {
+        constexpr month_weekday wdi = 2/Tuesday[3];
+        static_assert(wdi.month()           == February,   "");
+        static_assert(wdi.weekday_indexed() == Tuesday[3], "");
+        }
+    
+        for (int i = 1; i <= 12; ++i)
+            for (unsigned j = 0; j <= 6; ++j)
+            {
+                weekday_last wdi = weekday{j}[last];
+                month_weekday_last mwd1 = i/wdi;
+                month_weekday_last mwd2 = wdi/i;
+                assert(mwd1.month() == month(i));
+                assert(mwd1.weekday_last() == wdi);
+                assert(mwd2.month() == month(i));
+                assert(mwd2.weekday_last() == wdi);
+                assert(mwd1 == mwd2);
+            }
+    } 
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.operators/year_month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.operators/year_month.pass.cpp
new file mode 100644
index 000000000..3a85c1a59
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.operators/year_month.pass.cpp
@@ -0,0 +1,68 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+// constexpr year_month operator/(const year& y, const month& m) noexcept;
+//   Returns: {y, m}.
+// 
+// constexpr year_month operator/(const year& y, int m) noexcept;
+//   Returns: y / month(m).
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using month      = std::chrono::month;
+    using year       = std::chrono::year;
+    using year_month = std::chrono::year_month;
+
+    constexpr month February = std::chrono::February;
+
+    { // operator/(const year& y, const month& m)
+        ASSERT_NOEXCEPT (                     year{2018}/February);
+        ASSERT_SAME_TYPE(year_month, decltype(year{2018}/February));
+
+        static_assert((year{2018}/February).year()  == year{2018}, "");
+        static_assert((year{2018}/February).month() == month{2},   "");
+        for (int i = 1000; i <= 1030; ++i)
+            for (unsigned j = 1; j <= 12; ++j)
+            {
+                year_month ym = year{i}/month{j};
+                assert(static_cast<int>(ym.year())       == i);
+                assert(static_cast<unsigned>(ym.month()) == j);
+            }
+    }
+
+
+    { // operator/(const year& y, const int m)
+        ASSERT_NOEXCEPT (                     year{2018}/4);
+        ASSERT_SAME_TYPE(year_month, decltype(year{2018}/4));
+
+        static_assert((year{2018}/2).year()  == year{2018}, "");
+        static_assert((year{2018}/2).month() == month{2},   "");
+        
+        for (int i = 1000; i <= 1030; ++i)
+            for (unsigned j = 1; j <= 12; ++j)
+            {
+                year_month ym = year{i}/j;
+                assert(static_cast<int>(ym.year())       == i);
+                assert(static_cast<unsigned>(ym.month()) == j);
+            }
+    } 
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.operators/year_month_day.pass.cpp b/test/std/utilities/time/time.cal/time.cal.operators/year_month_day.pass.cpp
new file mode 100644
index 000000000..b34103a56
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.operators/year_month_day.pass.cpp
@@ -0,0 +1,192 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+// constexpr year_month_day
+//   operator/(const year_month& ym, const day& d) noexcept;
+// Returns: {ym.year(), ym.month(), d}.
+// 
+// constexpr year_month_day
+//   operator/(const year_month& ym, int d) noexcept;
+// Returns: ym / day(d).
+// 
+// constexpr year_month_day
+//   operator/(const year& y, const month_day& md) noexcept;
+// Returns: y / md.month() / md.day().
+// 
+// constexpr year_month_day
+//   operator/(int y, const month_day& md) noexcept;
+// Returns: year(y) / md.
+// 
+// constexpr year_month_day
+//   operator/(const month_day& md, const year& y) noexcept;
+// Returns: y / md.
+// 
+// constexpr year_month_day
+//   operator/(const month_day& md, int y) noexcept;
+// Returns: year(y) / md.
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+    using year_month     = std::chrono::year_month;
+    using month_day      = std::chrono::month_day;
+    using year_month_day = std::chrono::year_month_day;
+    using weekday        = std::chrono::weekday;
+
+    constexpr month February = std::chrono::February;
+    constexpr year_month Feb2018{year{2018}, February};
+
+    { // operator/(const year_month& ym, const day& d)
+        ASSERT_NOEXCEPT (                         Feb2018/day{2});
+        ASSERT_SAME_TYPE(year_month_day, decltype(Feb2018/day{2}));
+
+        static_assert((Feb2018/day{2}).month() == February, "");
+        static_assert((Feb2018/day{2}).day()   == day{2},   "");
+        
+        for (int i = 1000; i < 1010; ++i)
+            for (int j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 28; ++k)
+                {
+                    year y(i);
+                    month m(j);
+                    day d(k);
+                    year_month ym(y, m);
+                    year_month_day ymd = ym/d;
+                    assert(ymd.year()  == y);
+                    assert(ymd.month() == m);
+                    assert(ymd.day()   == d);
+                }
+    }
+
+
+    { // operator/(const year_month& ym, int d)
+        ASSERT_NOEXCEPT (                         Feb2018/2);
+        ASSERT_SAME_TYPE(year_month_day, decltype(Feb2018/2));
+
+        static_assert((Feb2018/2).month() == February, "");
+        static_assert((Feb2018/2).day()   == day{2},   "");
+        
+        for (int i = 1000; i < 1010; ++i)
+            for (int j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 28; ++k)
+                {
+                    year y(i);
+                    month m(j);
+                    day d(k);
+                    year_month ym(y, m);
+                    year_month_day ymd = ym/k;
+                    assert(ymd.year()  == y);
+                    assert(ymd.month() == m);
+                    assert(ymd.day()   == d);
+                }
+    }
+
+
+    { // operator/(const year_month& ym, int d)
+        ASSERT_NOEXCEPT (                         Feb2018/2);
+        ASSERT_SAME_TYPE(year_month_day, decltype(Feb2018/2));
+
+        static_assert((Feb2018/2).month() == February, "");
+        static_assert((Feb2018/2).day()   == day{2},   "");
+        
+        for (int i = 1000; i < 1010; ++i)
+            for (int j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 28; ++k)
+                {
+                    year y(i);
+                    month m(j);
+                    day d(k);
+                    year_month ym(y, m);
+                    year_month_day ymd = ym/k;
+                    assert(ymd.year()  == y);
+                    assert(ymd.month() == m);
+                    assert(ymd.day()   == d);
+                }
+    }
+
+
+
+
+    { // operator/(const year& y, const month_day& md) (and switched)
+        ASSERT_NOEXCEPT (                         year{2018}/month_day{February, day{2}});
+        ASSERT_SAME_TYPE(year_month_day, decltype(year{2018}/month_day{February, day{2}}));
+        ASSERT_NOEXCEPT (                         month_day{February, day{2}}/year{2018});
+        ASSERT_SAME_TYPE(year_month_day, decltype(month_day{February, day{2}}/year{2018}));
+
+        static_assert((year{2018}/month_day{February, day{2}}).month() == February, "" );
+        static_assert((year{2018}/month_day{February, day{2}}).day()   == day{2},   "" );
+        static_assert((month_day{February, day{2}}/year{2018}).month() == February, "" );
+        static_assert((month_day{February, day{2}}/year{2018}).day()   == day{2},   "" );
+        
+        for (int i = 1000; i < 1010; ++i)
+            for (int j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 28; ++k)
+                {
+                    year y(i);
+                    month m(j);
+                    day d(k);
+                    month_day md(m, d);
+                    year_month_day ymd1 = y/md;
+                    year_month_day ymd2 = md/y;
+                    assert(ymd1.year()  == y);
+                    assert(ymd2.year()  == y);
+                    assert(ymd1.month() == m);
+                    assert(ymd2.month() == m);
+                    assert(ymd1.day()   == d);
+                    assert(ymd2.day()   == d);
+                    assert(ymd1 == ymd2);
+                }
+    }
+
+    { // operator/(const month_day& md, int y) (and switched)
+        ASSERT_NOEXCEPT (                         2018/month_day{February, day{2}});
+        ASSERT_SAME_TYPE(year_month_day, decltype(2018/month_day{February, day{2}}));
+        ASSERT_NOEXCEPT (                         month_day{February, day{2}}/2018);
+        ASSERT_SAME_TYPE(year_month_day, decltype(month_day{February, day{2}}/2018));
+
+        static_assert((2018/month_day{February, day{2}}).month() == February, "" );
+        static_assert((2018/month_day{February, day{2}}).day()   == day{2},   "" );
+        static_assert((month_day{February, day{2}}/2018).month() == February, "" );
+        static_assert((month_day{February, day{2}}/2018).day()   == day{2},   "" );
+        
+        for (int i = 1000; i < 1010; ++i)
+            for (int j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 28; ++k)
+                {
+                    year y(i);
+                    month m(j);
+                    day d(k);
+                    month_day md(m, d);
+                    year_month_day ymd1 = i/md;
+                    year_month_day ymd2 = md/i;
+                    assert(ymd1.year()  == y);
+                    assert(ymd2.year()  == y);
+                    assert(ymd1.month() == m);
+                    assert(ymd2.month() == m);
+                    assert(ymd1.day()   == d);
+                    assert(ymd2.day()   == d);
+                    assert(ymd1 == ymd2);
+                }
+    }
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.operators/year_month_day_last.pass.cpp b/test/std/utilities/time/time.cal/time.cal.operators/year_month_day_last.pass.cpp
new file mode 100644
index 000000000..a237842ed
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.operators/year_month_day_last.pass.cpp
@@ -0,0 +1,129 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// <chrono>
+// class year_month_day_last;
+
+// constexpr year_month_day_last
+//   operator/(const year_month& ym, last_spec) noexcept;
+// Returns: {ym.year(), month_day_last{ym.month()}}.
+
+
+// constexpr year_month_day_last
+//   operator/(const year& y, const month_day_last& mdl) noexcept;
+// Returns: {y, mdl}.
+// 
+// constexpr year_month_day_last
+//   operator/(int y, const month_day_last& mdl) noexcept;
+// Returns: year(y) / mdl.
+// 
+// constexpr year_month_day_last
+//   operator/(const month_day_last& mdl, const year& y) noexcept;
+// Returns: y / mdl.
+// 
+// constexpr year_month_day_last
+//   operator/(const month_day_last& mdl, int y) noexcept;
+// Returns: year(y) / mdl.
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using month_weekday       = std::chrono::month_weekday;
+    using month               = std::chrono::month;
+    using year_month          = std::chrono::year_month;
+    using year                = std::chrono::year;
+    using weekday_last        = std::chrono::weekday_last;
+    using weekday             = std::chrono::weekday;
+    using month_weekday_last  = std::chrono::month_weekday_last;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+
+    constexpr month February = std::chrono::February;
+    constexpr std::chrono::last_spec last = std::chrono::last;
+    
+    { // operator/(const year_month& ym, last_spec)
+        constexpr year_month Feb2018{year{2018}, February};
+        
+        ASSERT_NOEXCEPT (                              Feb2018/last);
+        ASSERT_SAME_TYPE(year_month_day_last, decltype(Feb2018/last));
+
+        static_assert((Feb2018/last).year()  == year{2018}, "");
+        static_assert((Feb2018/last).month() == February,   "");
+
+        for (int i = 1000; i < 1010; ++i)
+            for (unsigned j = 1; j <= 12; ++j)
+            {
+                year y{i};                
+                month m{j};
+                year_month_day_last ymdl = year_month{y,m}/last;
+                assert(ymdl.year()  == y);
+                assert(ymdl.month() == m);
+            }
+    }
+
+
+    { // operator/(const year& y, const month_day_last& mdl) (and switched)
+        ASSERT_NOEXCEPT (                              year{2018}/month_day_last{February});
+        ASSERT_SAME_TYPE(year_month_day_last, decltype(year{2018}/month_day_last{February}));
+        ASSERT_NOEXCEPT (                              month_day_last{February}/year{2018});
+        ASSERT_SAME_TYPE(year_month_day_last, decltype(month_day_last{February}/year{2018}));
+
+        static_assert((year{2018}/month_day_last{February}).month() == February,   "");
+        static_assert((year{2018}/month_day_last{February}).year()  == year{2018}, "");
+        static_assert((month_day_last{February}/year{2018}).month() == February,   "");
+        static_assert((month_day_last{February}/year{2018}).year()  == year{2018}, "");
+    
+        for (int i = 1000; i < 1010; ++i)
+            for (unsigned j = 1; j <= 12; ++j)
+            {
+                year y{i};                
+                month m{j};
+                year_month_day_last ymdl1 = y/month_day_last{m};
+                year_month_day_last ymdl2 = month_day_last{m}/y;
+                assert(ymdl1.month() == m);
+                assert(ymdl2.month() == m);
+                assert(ymdl2.year()  == y);
+                assert(ymdl1.year()  == y);
+                assert(ymdl1 == ymdl2);
+            }
+    } 
+
+    { // operator/(int y, const month_day_last& mdl) (and switched)
+        ASSERT_NOEXCEPT (                              2018/month_day_last{February});
+        ASSERT_SAME_TYPE(year_month_day_last, decltype(2018/month_day_last{February}));
+        ASSERT_NOEXCEPT (                              month_day_last{February}/2018);
+        ASSERT_SAME_TYPE(year_month_day_last, decltype(month_day_last{February}/2018));
+
+        static_assert((2018/month_day_last{February}).month() == February,   "");
+        static_assert((2018/month_day_last{February}).year()  == year{2018}, "");
+        static_assert((month_day_last{February}/2018).month() == February,   "");
+        static_assert((month_day_last{February}/2018).year()  == year{2018}, "");
+    
+        for (int i = 1000; i < 1010; ++i)
+            for (unsigned j = 1; j <= 12; ++j)
+            {
+                year y{i};                
+                month m{j};
+                year_month_day_last ymdl1 = i/month_day_last{m};
+                year_month_day_last ymdl2 = month_day_last{m}/i;
+                assert(ymdl1.month() == m);
+                assert(ymdl2.month() == m);
+                assert(ymdl2.year()  == y);
+                assert(ymdl1.year()  == y);
+                assert(ymdl1 == ymdl2);
+            }
+    } 
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.operators/year_month_weekday.pass.cpp b/test/std/utilities/time/time.cal/time.cal.operators/year_month_weekday.pass.cpp
new file mode 100644
index 000000000..5299b5b37
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.operators/year_month_weekday.pass.cpp
@@ -0,0 +1,145 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr year_month_weekday
+//   operator/(const year_month& ym, const weekday_indexed& wdi) noexcept;
+// Returns: {ym.year(), ym.month(), wdi}.
+// 
+// constexpr year_month_weekday
+//   operator/(const year& y, const month_weekday& mwd) noexcept;
+// Returns: {y, mwd.month(), mwd.weekday_indexed()}.
+// 
+// constexpr year_month_weekday
+//   operator/(int y, const month_weekday& mwd) noexcept;
+// Returns: year(y) / mwd.
+// 
+// constexpr year_month_weekday
+//   operator/(const month_weekday& mwd, const year& y) noexcept;
+// Returns: y / mwd.
+// 
+// constexpr year_month_weekday
+//   operator/(const month_weekday& mwd, int y) noexcept;
+// Returns: year(y) / mwd.
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using year               = std::chrono::year;
+    using year_month         = std::chrono::year_month;
+    using month_weekday      = std::chrono::month_weekday;
+    using year_month_weekday = std::chrono::year_month_weekday;
+    using month              = std::chrono::month;
+    using weekday            = std::chrono::weekday;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    constexpr month February = std::chrono::February;
+
+    
+    { // operator/(const year_month& ym, const weekday_indexed& wdi)
+        constexpr year_month Feb2018{year{2018}, February};
+        
+        ASSERT_NOEXCEPT (                             Feb2018/weekday_indexed{Tuesday, 2});
+        ASSERT_SAME_TYPE(year_month_weekday, decltype(Feb2018/weekday_indexed{Tuesday, 2}));
+
+        static_assert((Feb2018/weekday_indexed{Tuesday, 2}).year()    == year{2018}, "" );
+        static_assert((Feb2018/weekday_indexed{Tuesday, 2}).month()   == February, "" );
+        static_assert((Feb2018/weekday_indexed{Tuesday, 2}).weekday() == Tuesday,  "" );
+
+        for (int i = 1000; i < 1010; ++i)
+            for (int j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 6; ++k)
+                    for (unsigned l = 1; l <= 5; ++l)
+                    {
+                        year y(i);
+                        month m(j);
+                        weekday wd{k};
+                        year_month_weekday ymd = year_month{y,m}/weekday_indexed{wd,l};
+                        assert(ymd.year()    == y);
+                        assert(ymd.month()   == m);
+                        assert(ymd.weekday() == wd);
+                    }
+    }
+
+    { // operator/(const year& y, const month_weekday& mwd) (and switched)
+        constexpr month_weekday Feb1stTues{February, weekday_indexed{Tuesday, 1}};
+        ASSERT_NOEXCEPT (                             year{2018}/Feb1stTues);
+        ASSERT_SAME_TYPE(year_month_weekday, decltype(year{2018}/Feb1stTues));
+        ASSERT_NOEXCEPT (                             Feb1stTues/year{2018});
+        ASSERT_SAME_TYPE(year_month_weekday, decltype(Feb1stTues/year{2018}));
+
+        static_assert((year{2018}/Feb1stTues).year()    == year{2018}, "" );
+        static_assert((year{2018}/Feb1stTues).month()   == February, "" );
+        static_assert((year{2018}/Feb1stTues).weekday() == Tuesday,  "" );
+
+        for (int i = 1000; i < 1010; ++i)
+            for (int j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 6; ++k)
+                    for (unsigned l = 1; l <= 5; ++l)
+                    {
+                        year y(i);
+                        month m(j);
+                        weekday wd{k};
+                        month_weekday mwd{m, weekday_indexed{weekday{k}, l}};
+                        year_month_weekday ymd1 = y/mwd;
+                        year_month_weekday ymd2 = mwd/y;
+                        assert(ymd1.year()    == y);
+                        assert(ymd2.year()    == y);
+                        assert(ymd1.month()   == m);
+                        assert(ymd2.month()   == m);
+                        assert(ymd1.weekday() == wd);
+                        assert(ymd2.weekday() == wd);
+                        assert(ymd1 == ymd2);
+                    }
+    }
+
+
+    { // operator/(int y, const month_weekday& mwd) (and switched)
+        constexpr month_weekday Feb1stTues{February, weekday_indexed{Tuesday, 1}};
+        ASSERT_NOEXCEPT (                             2018/Feb1stTues);
+        ASSERT_SAME_TYPE(year_month_weekday, decltype(2018/Feb1stTues));
+        ASSERT_NOEXCEPT (                             Feb1stTues/2018);
+        ASSERT_SAME_TYPE(year_month_weekday, decltype(Feb1stTues/2018));
+
+        static_assert((2018/Feb1stTues).year()    == year{2018}, "" );
+        static_assert((2018/Feb1stTues).month()   == February, "" );
+        static_assert((2018/Feb1stTues).weekday() == Tuesday,  "" );
+
+        for (int i = 1000; i < 1010; ++i)
+            for (int j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 6; ++k)
+                    for (unsigned l = 1; l <= 5; ++l)
+                    {
+                        year y(i);
+                        month m(j);
+                        weekday wd{k};
+                        month_weekday mwd{m, weekday_indexed{weekday{k}, l}};
+                        year_month_weekday ymd1 = i/mwd;
+                        year_month_weekday ymd2 = mwd/i;
+                        assert(ymd1.year()    == y);
+                        assert(ymd2.year()    == y);
+                        assert(ymd1.month()   == m);
+                        assert(ymd2.month()   == m);
+                        assert(ymd1.weekday() == wd);
+                        assert(ymd2.weekday() == wd);
+                        assert(ymd1 == ymd2);
+                    }
+     } 
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.operators/year_month_weekday_last.pass.cpp b/test/std/utilities/time/time.cal/time.cal.operators/year_month_weekday_last.pass.cpp
new file mode 100644
index 000000000..7ceaffaab
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.operators/year_month_weekday_last.pass.cpp
@@ -0,0 +1,154 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+// constexpr year_month_weekday_last
+//   operator/(const year_month& ym, const weekday_last& wdl) noexcept;
+// Returns: {ym.year(), ym.month(), wdl}.
+// 
+// constexpr year_month_weekday_last
+//   operator/(const year& y, const month_weekday_last& mwdl) noexcept;
+// Returns: {y, mwdl.month(), mwdl.weekday_last()}.
+// 
+// constexpr year_month_weekday_last
+//   operator/(int y, const month_weekday_last& mwdl) noexcept;
+// Returns: year(y) / mwdl.
+// 
+// constexpr year_month_weekday_last
+//   operator/(const month_weekday_last& mwdl, const year& y) noexcept;
+// Returns: y / mwdl.
+// 
+// constexpr year_month_weekday_last
+//   operator/(const month_weekday_last& mwdl, int y) noexcept;
+// Returns: year(y) / mwdl.
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using year_month         = std::chrono::year_month;
+    using month_weekday      = std::chrono::month_weekday;
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using weekday            = std::chrono::weekday;
+    using weekday_last       = std::chrono::weekday_last;
+    using month_weekday_last = std::chrono::month_weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    constexpr month February = std::chrono::February;
+    
+    { // operator/(const year_month& ym, const weekday_last& wdl) (and switched)
+        constexpr year_month Feb2018{year{2018}, February};
+
+        ASSERT_NOEXCEPT (                                  Feb2018/weekday_last{Tuesday});
+        ASSERT_SAME_TYPE(year_month_weekday_last, decltype(Feb2018/weekday_last{Tuesday}));
+
+        static_assert((Feb2018/weekday_last{Tuesday}).year()    == year{2018}, "");
+        static_assert((Feb2018/weekday_last{Tuesday}).month()   == February,   "");
+        static_assert((Feb2018/weekday_last{Tuesday}).weekday() == Tuesday,    "");
+    
+        for (int i = 1000; i < 1010; ++i)
+            for (unsigned j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 6; ++k)
+                {
+                    year y{i};
+                    month m{j};
+                    weekday wd{k};
+                    year_month_weekday_last ymwdl = year_month{y,m}/weekday_last{wd};
+                    assert(ymwdl.year()    == y);
+                    assert(ymwdl.month()   == m);
+                    assert(ymwdl.weekday() == wd);
+                }
+    }
+
+
+    { // operator/(const year& y, const month_weekday_last& mwdl) (and switched)
+        constexpr month_weekday_last FebLastTues{February, weekday_last{Tuesday}};
+        
+        ASSERT_NOEXCEPT (                                  year{2018}/FebLastTues);
+        ASSERT_SAME_TYPE(year_month_weekday_last, decltype(year{2018}/FebLastTues));
+        ASSERT_NOEXCEPT (                                  FebLastTues/year{2018});
+        ASSERT_SAME_TYPE(year_month_weekday_last, decltype(FebLastTues/year{2018}));
+
+
+        static_assert((year{2018}/FebLastTues).year()    == year{2018}, "");
+        static_assert((year{2018}/FebLastTues).month()   == February,   "");
+        static_assert((year{2018}/FebLastTues).weekday() == Tuesday,    "");
+        static_assert((FebLastTues/year{2018}).year()    == year{2018}, "");
+        static_assert((FebLastTues/year{2018}).month()   == February,   "");
+        static_assert((FebLastTues/year{2018}).weekday() == Tuesday,    "");
+
+
+        for (int i = 1000; i < 1010; ++i)
+            for (unsigned j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 6; ++k)
+                {
+                    year y{i};
+                    month m{j};
+                    weekday wd{k};
+                    year_month_weekday_last ymwdl1 = y/month_weekday_last{m, weekday_last{wd}};
+                    year_month_weekday_last ymwdl2 = month_weekday_last{m, weekday_last{wd}}/y;
+                    assert(ymwdl1.year()    == y);
+                    assert(ymwdl2.year()    == y);
+                    assert(ymwdl1.month()   == m);
+                    assert(ymwdl2.month()   == m);
+                    assert(ymwdl1.weekday() == wd);
+                    assert(ymwdl2.weekday() == wd);
+                    assert(ymwdl1 == ymwdl2);
+                }
+    }
+
+
+    { // operator/(int y, const month_weekday_last& mwdl) (and switched)
+        constexpr month_weekday_last FebLastTues{February, weekday_last{Tuesday}};
+        
+        ASSERT_NOEXCEPT (                                  2018/FebLastTues);
+        ASSERT_SAME_TYPE(year_month_weekday_last, decltype(2018/FebLastTues));
+        ASSERT_NOEXCEPT (                                  FebLastTues/2018);
+        ASSERT_SAME_TYPE(year_month_weekday_last, decltype(FebLastTues/2018));
+
+
+        static_assert((2018/FebLastTues).year()    == year{2018}, "");
+        static_assert((2018/FebLastTues).month()   == February,   "");
+        static_assert((2018/FebLastTues).weekday() == Tuesday,    "");
+        static_assert((FebLastTues/2018).year()    == year{2018}, "");
+        static_assert((FebLastTues/2018).month()   == February,   "");
+        static_assert((FebLastTues/2018).weekday() == Tuesday,    "");
+
+
+        for (int i = 1000; i < 1010; ++i)
+            for (unsigned j = 1; j <= 12; ++j)
+                for (unsigned k = 0; k <= 6; ++k)
+                {
+                    year y{i};
+                    month m{j};
+                    weekday wd{k};
+                    year_month_weekday_last ymwdl1 = i/month_weekday_last{m, weekday_last{wd}};
+                    year_month_weekday_last ymwdl2 = month_weekday_last{m, weekday_last{wd}}/i;
+                    assert(ymwdl1.year()    == y);
+                    assert(ymwdl2.year()    == y);
+                    assert(ymwdl1.month()   == m);
+                    assert(ymwdl2.month()   == m);
+                    assert(ymwdl1.weekday() == wd);
+                    assert(ymwdl2.weekday() == wd);
+                    assert(ymwdl1 == ymwdl2);
+                }
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/ctor.pass.cpp
new file mode 100644
index 000000000..4c13bdef8
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/ctor.pass.cpp
@@ -0,0 +1,61 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_indexed;
+
+//                     weekday_indexed() = default;
+//  constexpr weekday_indexed(const chrono::weekday& wd, unsigned index) noexcept;
+//
+//  Effects: Constructs an object of type weekday_indexed by initializing wd_ with wd and index_ with index.
+//    The values held are unspecified if !wd.ok() or index is not in the range [1, 5].
+//
+//  constexpr chrono::weekday weekday() const noexcept;
+//  constexpr unsigned        index()   const noexcept;
+//  constexpr bool ok()                 const noexcept;
+         
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday  = std::chrono::weekday;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    ASSERT_NOEXCEPT(weekday_indexed{});
+    ASSERT_NOEXCEPT(weekday_indexed(weekday{1}, 1));
+    
+    constexpr weekday_indexed wdi0{};
+    static_assert( wdi0.weekday() == weekday{}, "");
+    static_assert( wdi0.index() == 0,           "");
+    static_assert(!wdi0.ok(),                   "");
+
+    constexpr weekday_indexed wdi1{std::chrono::Sunday, 2};
+    static_assert( wdi1.weekday() == std::chrono::Sunday, "");
+    static_assert( wdi1.index() == 2,                     "");
+    static_assert( wdi1.ok(),                             "");
+    
+    for (unsigned i = 1; i <= 5; ++i)
+    {
+        weekday_indexed wdi(std::chrono::Tuesday, i);
+        assert( wdi.weekday() == std::chrono::Tuesday);
+        assert( wdi.index() == i);
+        assert( wdi.ok());
+    }
+
+    for (unsigned i = 6; i <= 20; ++i)
+    {
+        weekday_indexed wdi(std::chrono::Tuesday, i);
+        assert(!wdi.ok());
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/index.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/index.pass.cpp
new file mode 100644
index 000000000..0d03dbbcb
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/index.pass.cpp
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_indexed;
+
+// constexpr unsigned index() const noexcept;
+//  Returns: index_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday         = std::chrono::weekday;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    ASSERT_NOEXCEPT(                    std::declval<const weekday_indexed>().index());
+    ASSERT_SAME_TYPE(unsigned, decltype(std::declval<const weekday_indexed>().index()));
+
+    static_assert( weekday_indexed{}.index() == 0, "");
+
+    for (unsigned i = 1; i <= 5; ++i)
+    {
+        weekday_indexed wdi(weekday{2}, i);
+        assert( static_cast<unsigned>(wdi.index()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/ok.pass.cpp
new file mode 100644
index 000000000..e0277f656
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/ok.pass.cpp
@@ -0,0 +1,49 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_indexed;
+
+// constexpr bool ok() const noexcept;
+//  Returns: wd_.ok() && 1 <= index_ && index_ <= 5
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday         = std::chrono::weekday;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    ASSERT_NOEXCEPT(                std::declval<const weekday_indexed>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const weekday_indexed>().ok()));
+
+    static_assert(!weekday_indexed{}.ok(),                       "");
+    static_assert( weekday_indexed{std::chrono::Sunday, 2}.ok(), "");
+
+    assert(!(weekday_indexed(std::chrono::Tuesday, 0).ok()));
+    for (unsigned i = 1; i <= 5; ++i)
+    {
+        weekday_indexed wdi(std::chrono::Tuesday, i);
+        assert( wdi.ok());
+    }
+
+    for (unsigned i = 6; i <= 20; ++i)
+    {
+        weekday_indexed wdi(std::chrono::Tuesday, i);
+        assert(!wdi.ok());
+    }
+
+//  Not a valid weekday
+    assert(!(weekday_indexed(weekday{9U}, 1).ok()));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/weekday.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/weekday.pass.cpp
new file mode 100644
index 000000000..484c19cca
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.members/weekday.pass.cpp
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_indexed;
+
+// constexpr chrono::weekday weekday() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday         = std::chrono::weekday;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    ASSERT_NOEXCEPT(                                std::declval<const weekday_indexed>().weekday());
+    ASSERT_SAME_TYPE(std::chrono::weekday, decltype(std::declval<const weekday_indexed>().weekday()));
+
+    static_assert( weekday_indexed{}.weekday() == weekday{},                                   "");
+    static_assert( weekday_indexed{std::chrono::Tuesday, 0}.weekday() == std::chrono::Tuesday, "");
+
+    for (unsigned i = 0; i <= 6; ++i)
+    {
+        weekday_indexed wdi(weekday{i}, 2);
+        assert( static_cast<unsigned>(wdi.weekday()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..acaca806a
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_indexed;
+
+// constexpr bool operator==(const weekday_indexed& x, const weekday_indexed& y) noexcept;
+//   Returns: x.weekday() == y.weekday() && x.index() == y.index().
+// constexpr bool operator!=(const weekday_indexed& x, const weekday_indexed& y) noexcept;
+//   Returns: !(x == y)
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using weekday         = std::chrono::weekday;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    AssertComparisons2AreNoexcept<weekday_indexed>();
+    AssertComparisons2ReturnBool<weekday_indexed>();
+    
+    static_assert( (weekday_indexed{} == weekday_indexed{}), "");
+    static_assert(!(weekday_indexed{} != weekday_indexed{}), "");
+
+    static_assert(!(weekday_indexed{} == weekday_indexed{std::chrono::Tuesday, 1}), "");
+    static_assert( (weekday_indexed{} != weekday_indexed{std::chrono::Tuesday, 1}), "");
+    
+//  Some 'ok' values as well
+    static_assert( (weekday_indexed{weekday{1}, 2} == weekday_indexed{weekday{1}, 2}), "");
+    static_assert(!(weekday_indexed{weekday{1}, 2} != weekday_indexed{weekday{1}, 2}), "");
+
+    static_assert(!(weekday_indexed{weekday{1}, 2} == weekday_indexed{weekday{1}, 1}), "");
+    static_assert( (weekday_indexed{weekday{1}, 2} != weekday_indexed{weekday{1}, 1}), "");
+    static_assert(!(weekday_indexed{weekday{1}, 2} == weekday_indexed{weekday{2}, 2}),  "");
+    static_assert( (weekday_indexed{weekday{1}, 2} != weekday_indexed{weekday{2}, 2}),  "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..9938b8a68
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdidx/time.cal.wdidx.nonmembers/streaming.pass.cpp
@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class weekday_indexed;
+
+// template<class charT, class traits>
+//   basic_ostream<charT, traits>&
+//   operator<<(basic_ostream<charT, traits>& os, const weekday_indexed& wdi);
+//
+//   Effects: os << wdi.weekday() << '[' << wdi.index(). 
+//     If wdi.index() is in the range [1, 5], appends with ']', 
+//       otherwise appends with " is not a valid index]".
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday_indexed = std::chrono::weekday_indexed;
+    using weekday         = std::chrono::weekday;
+    
+    std::cout << weekday_indexed{weekday{3}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdidx/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdidx/types.pass.cpp
new file mode 100644
index 000000000..8b2e70e5e
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdidx/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_indexed;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday_indexed = std::chrono::weekday_indexed;
+    
+    static_assert(std::is_trivially_copyable_v<weekday_indexed>, "");
+    static_assert(std::is_standard_layout_v<weekday_indexed>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.members/ctor.pass.cpp
new file mode 100644
index 000000000..facc1dc08
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.members/ctor.pass.cpp
@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_last;
+
+//  explicit constexpr weekday_last(const chrono::weekday& wd) noexcept;
+//
+//  Effects: Constructs an object of type weekday_last by initializing wd_ with wd.
+//
+//  constexpr chrono::weekday weekday() const noexcept;
+//  constexpr bool ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday      = std::chrono::weekday;
+    using weekday_last = std::chrono::weekday_last;
+
+    ASSERT_NOEXCEPT(weekday_last{weekday{}});
+    
+    constexpr weekday_last wdl0{weekday{}};
+    static_assert( wdl0.weekday() == weekday{}, "");
+    static_assert( wdl0.ok(),                   "");
+
+    constexpr weekday_last wdl1 {weekday{1}};
+    static_assert( wdl1.weekday() == weekday{1}, "");
+    static_assert( wdl1.ok(),                    "");
+    
+    for (unsigned i = 0; i <= 255; ++i)
+    {
+        weekday_last wdl{weekday{i}};
+        assert(wdl.weekday() == weekday{i});
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.members/ok.pass.cpp
new file mode 100644
index 000000000..7c842b150
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.members/ok.pass.cpp
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_last;
+
+//  constexpr bool ok() const noexcept;
+//  Returns: wd_.ok()
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday      = std::chrono::weekday;
+    using weekday_last = std::chrono::weekday_last;
+
+    ASSERT_NOEXCEPT(                std::declval<const weekday_last>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const weekday_last>().ok()));
+
+    static_assert( weekday_last{weekday{0}}.ok(), "");
+    static_assert( weekday_last{weekday{1}}.ok(), "");
+    static_assert(!weekday_last{weekday{7}}.ok(), "");
+
+    for (unsigned i = 0; i <= 255; ++i)
+        assert(weekday_last{weekday{i}}.ok() == weekday{i}.ok());
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.members/weekday.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.members/weekday.pass.cpp
new file mode 100644
index 000000000..191f23e92
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.members/weekday.pass.cpp
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_last;
+
+//  constexpr chrono::weekday weekday() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday      = std::chrono::weekday;
+    using weekday_last = std::chrono::weekday_last;
+
+    ASSERT_NOEXCEPT(                   std::declval<const weekday_last>().weekday());
+    ASSERT_SAME_TYPE(weekday, decltype(std::declval<const weekday_last>().weekday()));
+
+    for (unsigned i = 0; i <= 255; ++i)
+        assert(weekday_last{weekday{i}}.weekday() == weekday{i});
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..180a0a3c3
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_last;
+
+// constexpr bool operator==(const weekday& x, const weekday& y) noexcept;
+// constexpr bool operator!=(const weekday& x, const weekday& y) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using weekday      = std::chrono::weekday;
+    using weekday_last = std::chrono::weekday_last;
+
+    AssertComparisons2AreNoexcept<weekday_last>();
+    AssertComparisons2ReturnBool<weekday_last>();
+    
+    static_assert(testComparisons2Values<weekday_last>(weekday{0}, weekday{0}), "");
+    static_assert(testComparisons2Values<weekday_last>(weekday{0}, weekday{1}), "");
+    
+//  Some 'ok' values as well
+    static_assert(testComparisons2Values<weekday_last>(weekday{2}, weekday{2}), "");
+    static_assert(testComparisons2Values<weekday_last>(weekday{2}, weekday{3}), "");
+    
+    for (unsigned i = 0; i < 6; ++i)
+        for (unsigned j = 0; j < 6; ++j)
+            assert(testComparisons2Values<weekday_last>(weekday{i}, weekday{j}));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..618544344
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdlast/time.cal.wdlast.nonmembers/streaming.pass.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class weekday_last;
+
+//   template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const weekday_last& wdl);
+// 
+//   Returns: os << wdl.weekday() << "[last]".
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+   using weekday_last = std::chrono::weekday_last;
+   using weekday      = std::chrono::weekday;
+   
+   std::cout << weekday_last{weekday{3}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.wdlast/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.wdlast/types.pass.cpp
new file mode 100644
index 000000000..51bc8f965
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.wdlast/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday_last;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday_last = std::chrono::weekday_last;
+    
+    static_assert(std::is_trivially_copyable_v<weekday_last>, "");
+    static_assert(std::is_standard_layout_v<weekday_last>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/ctor.pass.cpp
new file mode 100644
index 000000000..95e498549
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/ctor.pass.cpp
@@ -0,0 +1,51 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday;
+
+//                     weekday() = default;
+//  explicit constexpr weekday(unsigned wd) noexcept;
+//  constexpr weekday(const sys_days& dp) noexcept;
+//  explicit constexpr weekday(const local_days& dp) noexcept;
+//
+//  explicit constexpr operator unsigned() const noexcept;
+
+//  Effects: Constructs an object of type weekday by initializing m_ with m.
+//    The value held is unspecified if d is not in the range [0, 255].
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday = std::chrono::weekday;
+
+    ASSERT_NOEXCEPT(weekday{});
+    ASSERT_NOEXCEPT(weekday(1));
+    ASSERT_NOEXCEPT(static_cast<unsigned>(weekday(1)));
+    
+    constexpr weekday m0{};
+    static_assert(static_cast<unsigned>(m0) == 0, "");
+
+    constexpr weekday m1{1};
+    static_assert(static_cast<unsigned>(m1) == 1, "");
+    
+    for (unsigned i = 0; i <= 255; ++i)
+    {
+        weekday m(i);
+        assert(static_cast<unsigned>(m) == i);
+    }
+
+// TODO - sys_days and local_days ctor tests
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/decrement.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/decrement.pass.cpp
new file mode 100644
index 000000000..213e7282d
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/decrement.pass.cpp
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday;
+
+//  constexpr weekday& operator--() noexcept;
+//  constexpr weekday operator--(int) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "../../euclidian.h"
+
+template <typename WD>
+constexpr bool testConstexpr()
+{
+    WD wd{1};
+    if (static_cast<unsigned>(--wd) != 0) return false;
+    if (static_cast<unsigned>(wd--) != 0) return false;
+    if (static_cast<unsigned>(wd)   != 6) return false;
+    return true;
+}
+
+int main()
+{
+    using weekday = std::chrono::weekday;
+    ASSERT_NOEXCEPT(--(std::declval<weekday&>())  );
+    ASSERT_NOEXCEPT(  (std::declval<weekday&>())--);
+
+    ASSERT_SAME_TYPE(weekday , decltype(  std::declval<weekday&>()--));
+    ASSERT_SAME_TYPE(weekday&, decltype(--std::declval<weekday&>()  ));
+    
+    static_assert(testConstexpr<weekday>(), "");
+
+    for (unsigned i = 0; i <= 6; ++i)
+    {
+        weekday wd(i);
+        assert((static_cast<unsigned>(--wd) == euclidian_subtraction<unsigned, 0, 6>(i, 1)));
+        assert((static_cast<unsigned>(wd--) == euclidian_subtraction<unsigned, 0, 6>(i, 1)));
+        assert((static_cast<unsigned>(wd)   == euclidian_subtraction<unsigned, 0, 6>(i, 2)));
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/increment.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/increment.pass.cpp
new file mode 100644
index 000000000..171053a94
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/increment.pass.cpp
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday;
+
+//  constexpr weekday& operator++() noexcept;
+//  constexpr weekday operator++(int) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "../../euclidian.h"
+
+template <typename WD>
+constexpr bool testConstexpr()
+{
+    WD wd{5};
+    if (static_cast<unsigned>(++wd) != 6) return false;
+    if (static_cast<unsigned>(wd++) != 6) return false;
+    if (static_cast<unsigned>(wd)   != 0) return false;
+    return true;
+}
+
+int main()
+{
+    using weekday = std::chrono::weekday;
+    ASSERT_NOEXCEPT(++(std::declval<weekday&>())  );
+    ASSERT_NOEXCEPT(  (std::declval<weekday&>())++);
+
+    ASSERT_SAME_TYPE(weekday , decltype(  std::declval<weekday&>()++));
+    ASSERT_SAME_TYPE(weekday&, decltype(++std::declval<weekday&>()  ));
+    
+    static_assert(testConstexpr<weekday>(), "");
+
+    for (unsigned i = 0; i <= 6; ++i)
+    {
+        weekday wd(i);
+        assert((static_cast<unsigned>(++wd) == euclidian_addition<unsigned, 0, 6>(i, 1)));
+        assert((static_cast<unsigned>(wd++) == euclidian_addition<unsigned, 0, 6>(i, 1)));
+        assert((static_cast<unsigned>(wd)   == euclidian_addition<unsigned, 0, 6>(i, 2)));
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/ok.pass.cpp
new file mode 100644
index 000000000..82ae2b3b5
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/ok.pass.cpp
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday;
+
+//  constexpr bool ok() const noexcept;
+//  Returns: wd_ <= 6
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday = std::chrono::weekday;
+
+    ASSERT_NOEXCEPT(                std::declval<const weekday>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const weekday>().ok()));
+
+    static_assert( weekday{0}.ok(), "");
+    static_assert( weekday{1}.ok(), "");
+    static_assert(!weekday{7}.ok(), "");
+
+    for (unsigned i = 0; i <= 6; ++i)
+        assert(weekday{i}.ok());
+    for (unsigned i = 7; i <= 255; ++i)
+        assert(!weekday{i}.ok());
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/operator[].pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/operator[].pass.cpp
new file mode 100644
index 000000000..4b66e7ad8
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/operator[].pass.cpp
@@ -0,0 +1,59 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday;
+
+//   constexpr weekday_indexed operator[](unsigned index) const noexcept;
+//   constexpr weekday_last    operator[](last_spec)      const noexcept;
+  
+  
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "../../euclidian.h"
+
+int main()
+{
+    using weekday         = std::chrono::weekday;
+    using weekday_last    = std::chrono::weekday_last;
+    using weekday_indexed = std::chrono::weekday_indexed;
+
+    constexpr weekday Sunday = std::chrono::Sunday;
+
+    ASSERT_NOEXCEPT(                           std::declval<weekday>()[1U]);
+    ASSERT_SAME_TYPE(weekday_indexed, decltype(std::declval<weekday>()[1U]));
+
+    ASSERT_NOEXCEPT(                           std::declval<weekday>()[std::chrono::last]);
+    ASSERT_SAME_TYPE(weekday_last,    decltype(std::declval<weekday>()[std::chrono::last]));
+    
+    static_assert(Sunday[2].weekday() == Sunday, "");
+    static_assert(Sunday[2].index  () == 2, "");
+
+    for (unsigned i = 0; i <= 6; ++i)
+    {
+        weekday wd(i);
+        weekday_last wdl = wd[std::chrono::last];
+        assert(wdl.weekday() == wd);
+        assert(wdl.ok());
+    }
+
+    for (unsigned i = 0; i <= 6; ++i)
+        for (unsigned j = 1; j <= 5; ++j)
+    {
+        weekday wd(i);
+        weekday_indexed wdi = wd[j];
+        assert(wdi.weekday() == wd);
+        assert(wdi.index() == j);
+        assert(wdi.ok());
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/plus_minus_equal.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/plus_minus_equal.pass.cpp
new file mode 100644
index 000000000..32d2289f1
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.members/plus_minus_equal.pass.cpp
@@ -0,0 +1,63 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday;
+
+// constexpr weekday& operator+=(const days& d) noexcept;
+// constexpr weekday& operator-=(const days& d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "../../euclidian.h"
+
+template <typename M, typename Ms>
+constexpr bool testConstexpr()
+{
+    M m1{1};
+    if (static_cast<unsigned>(m1 += Ms{ 1}) !=  2) return false;
+    if (static_cast<unsigned>(m1 += Ms{ 2}) !=  4) return false;
+    if (static_cast<unsigned>(m1 += Ms{ 4}) !=  1) return false;
+    if (static_cast<unsigned>(m1 -= Ms{ 1}) !=  0) return false;
+    if (static_cast<unsigned>(m1 -= Ms{ 2}) !=  5) return false;
+    if (static_cast<unsigned>(m1 -= Ms{ 4}) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using weekday = std::chrono::weekday;
+    using days    = std::chrono::days;
+
+    ASSERT_NOEXCEPT(                    std::declval<weekday&>() += std::declval<days&>());
+    ASSERT_SAME_TYPE(weekday&, decltype(std::declval<weekday&>() += std::declval<days&>()));
+
+    ASSERT_NOEXCEPT(                    std::declval<weekday&>() -= std::declval<days&>());
+    ASSERT_SAME_TYPE(weekday&, decltype(std::declval<weekday&>() -= std::declval<days&>()));
+    
+    static_assert(testConstexpr<weekday, days>(), "");
+
+    for (unsigned i = 0; i <= 6; ++i)
+    {
+        weekday wd(i);
+        assert((static_cast<unsigned>(wd += days{3}) == euclidian_addition<unsigned, 0, 6>(i, 3)));
+        assert((static_cast<unsigned>(wd)            == euclidian_addition<unsigned, 0, 6>(i, 3)));
+    }
+
+    for (unsigned i = 0; i <= 6; ++i)
+    {
+        weekday wd(i);
+        assert((static_cast<unsigned>(wd -= days{4}) == euclidian_subtraction<unsigned, 0, 6>(i, 4)));
+        assert((static_cast<unsigned>(wd)            == euclidian_subtraction<unsigned, 0, 6>(i, 4)));
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..65df8aee1
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday;
+
+// constexpr bool operator==(const weekday& x, const weekday& y) noexcept;
+// constexpr bool operator!=(const weekday& x, const weekday& y) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using weekday = std::chrono::weekday;
+
+    AssertComparisons2AreNoexcept<weekday>();
+    AssertComparisons2ReturnBool<weekday>();
+    
+    static_assert(testComparisons2Values<weekday>(0U ,0U), "");
+    static_assert(testComparisons2Values<weekday>(0U, 1U), "");
+    
+//  Some 'ok' values as well
+    static_assert(testComparisons2Values<weekday>(5U, 5U), "");
+    static_assert(testComparisons2Values<weekday>(5U, 2U), "");
+    
+    for (unsigned i = 0; i < 6; ++i)
+        for (unsigned j = 0; j < 6; ++j)
+            assert(testComparisons2Values<weekday>(i, j));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/literals.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/literals.pass.cpp
new file mode 100644
index 000000000..2bf676c7c
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/literals.pass.cpp
@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// inline constexpr weekday   Sunday{0};
+// inline constexpr weekday   Monday{1};
+// inline constexpr weekday   Tuesday{2};
+// inline constexpr weekday   Wednesday{3};
+// inline constexpr weekday   Thursday{4};
+// inline constexpr weekday   Friday{5};
+// inline constexpr weekday   Saturday{6};
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+
+    ASSERT_SAME_TYPE(const std::chrono::weekday, decltype(std::chrono::Sunday));
+    ASSERT_SAME_TYPE(const std::chrono::weekday, decltype(std::chrono::Monday));
+    ASSERT_SAME_TYPE(const std::chrono::weekday, decltype(std::chrono::Tuesday));
+    ASSERT_SAME_TYPE(const std::chrono::weekday, decltype(std::chrono::Wednesday));
+    ASSERT_SAME_TYPE(const std::chrono::weekday, decltype(std::chrono::Thursday));
+    ASSERT_SAME_TYPE(const std::chrono::weekday, decltype(std::chrono::Friday));
+    ASSERT_SAME_TYPE(const std::chrono::weekday, decltype(std::chrono::Saturday));
+
+    static_assert( std::chrono::Sunday    == std::chrono::weekday(0),  "");
+    static_assert( std::chrono::Monday    == std::chrono::weekday(1),  "");
+    static_assert( std::chrono::Tuesday   == std::chrono::weekday(2),  "");
+    static_assert( std::chrono::Wednesday == std::chrono::weekday(3),  "");
+    static_assert( std::chrono::Thursday  == std::chrono::weekday(4),  "");
+    static_assert( std::chrono::Friday    == std::chrono::weekday(5),  "");
+    static_assert( std::chrono::Saturday  == std::chrono::weekday(6),  "");
+
+    assert(std::chrono::Sunday    == std::chrono::weekday(0));
+    assert(std::chrono::Monday    == std::chrono::weekday(1));
+    assert(std::chrono::Tuesday   == std::chrono::weekday(2));
+    assert(std::chrono::Wednesday == std::chrono::weekday(3));
+    assert(std::chrono::Thursday  == std::chrono::weekday(4));
+    assert(std::chrono::Friday    == std::chrono::weekday(5));
+    assert(std::chrono::Saturday  == std::chrono::weekday(6));
+
+    assert(static_cast<unsigned>(std::chrono::Sunday)    ==  0);
+    assert(static_cast<unsigned>(std::chrono::Monday)    ==  1);
+    assert(static_cast<unsigned>(std::chrono::Tuesday)   ==  2);
+    assert(static_cast<unsigned>(std::chrono::Wednesday) ==  3);
+    assert(static_cast<unsigned>(std::chrono::Thursday)  ==  4);
+    assert(static_cast<unsigned>(std::chrono::Friday)    ==  5);
+    assert(static_cast<unsigned>(std::chrono::Saturday)  ==  6);
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/minus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/minus.pass.cpp
new file mode 100644
index 000000000..78734e504
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/minus.pass.cpp
@@ -0,0 +1,76 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday;
+
+// constexpr weekday operator-(const weekday& x, const days& y) noexcept;
+//   Returns: x + -y.
+//
+// constexpr days operator-(const weekday& x, const weekday& y) noexcept;
+// Returns: If x.ok() == true and y.ok() == true, returns a value d in the range
+//    [days{0}, days{6}] satisfying y + d == x. 
+// Otherwise the value returned is unspecified.
+// [Example: Sunday - Monday == days{6}. —end example]
+
+
+extern "C" int printf(const char *, ...);
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "../../euclidian.h"
+
+template <typename WD, typename Ds>
+constexpr bool testConstexpr()
+{
+    {
+    WD wd{5};
+    Ds offset{3};
+    if (wd - offset != WD{2}) return false;
+    if (wd - WD{2} != offset) return false;
+    }
+
+//  Check the example
+    if (WD{0} - WD{1} != Ds{6}) return false;
+    return true;
+}
+
+int main()
+{
+    using weekday  = std::chrono::weekday;
+    using days     = std::chrono::days;
+
+    ASSERT_NOEXCEPT(                   std::declval<weekday>() - std::declval<days>());
+    ASSERT_SAME_TYPE(weekday, decltype(std::declval<weekday>() - std::declval<days>()));
+
+    ASSERT_NOEXCEPT(                   std::declval<weekday>() - std::declval<weekday>());
+    ASSERT_SAME_TYPE(days,    decltype(std::declval<weekday>() - std::declval<weekday>()));
+    
+    static_assert(testConstexpr<weekday, days>(), "");
+
+    for (unsigned i = 0; i <= 6; ++i)
+        for (unsigned j = 0; j <= 6; ++j)
+        {
+            weekday wd = weekday{i} - days{j};
+            assert(wd + days{j} == weekday{i});
+            assert((static_cast<unsigned>(wd) == euclidian_subtraction<unsigned, 0, 6>(i, j)));
+        }
+
+    for (unsigned i = 0; i <= 6; ++i)
+        for (unsigned j = 0; j <= 6; ++j)
+        {
+            days d = weekday{j} - weekday{i};
+            assert(weekday{i} + d == weekday{j});
+        }
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/plus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/plus.pass.cpp
new file mode 100644
index 000000000..b7ef53f80
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/plus.pass.cpp
@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday;
+
+// constexpr weekday operator+(const days& x, const weekday& y) noexcept;
+//   Returns: weekday(int{x} + y.count()).
+//
+// constexpr weekday operator+(const weekday& x, const days& y) noexcept;
+//   Returns:
+//      weekday{modulo(static_cast<long long>(unsigned{x}) + y.count(), 7)}
+//   where modulo(n, 7) computes the remainder of n divided by 7 using Euclidean division. 
+//   [Note: Given a divisor of 12, Euclidean division truncates towards negative infinity
+//   and always produces a remainder in the range of [0, 6]. 
+//   Assuming no overflow in the signed summation, this operation results in a weekday
+//   holding a value in the range [0, 6] even if !x.ok(). —end note]
+//   [Example: Monday + days{6} == Sunday. —end example]
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "../../euclidian.h"
+
+template <typename M, typename Ms>
+constexpr bool testConstexpr()
+{
+    M m{1};
+    Ms offset{4};
+    if (m + offset != M{5}) return false;
+    if (offset + m != M{5}) return false;
+//  Check the example
+    if (M{1} + Ms{6} != M{0}) return false;
+    return true;
+}
+
+int main()
+{
+    using weekday = std::chrono::weekday;
+    using days    = std::chrono::days;
+
+    ASSERT_NOEXCEPT(                   std::declval<weekday>() + std::declval<days>());
+    ASSERT_SAME_TYPE(weekday, decltype(std::declval<weekday>() + std::declval<days>()));
+
+    ASSERT_NOEXCEPT(                   std::declval<days>() + std::declval<weekday>());
+    ASSERT_SAME_TYPE(weekday, decltype(std::declval<days>() + std::declval<weekday>()));
+    
+    static_assert(testConstexpr<weekday, days>(), "");
+
+    for (unsigned i = 0; i <= 6; ++i)
+        for (unsigned j = 0; j <= 6; ++j)
+        {
+            weekday wd1 = weekday{i} + days{j};
+            weekday wd2 = days{j} + weekday{i};
+            assert(wd1 == wd2);
+            assert((static_cast<unsigned>(wd1) == euclidian_addition<unsigned, 0, 6>(i, j)));
+            assert((static_cast<unsigned>(wd2) == euclidian_addition<unsigned, 0, 6>(i, j)));
+        }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..39cc3b81b
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/time.cal.weekday.nonmembers/streaming.pass.cpp
@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class weekday;
+
+// template<class charT, class traits>
+//   basic_ostream<charT, traits>&
+//   operator<<(basic_ostream<charT, traits>& os, const weekday& wd);
+// 
+//   Effects: If wd.ok() == true inserts format(os.getloc(), fmt, wd) where fmt is "%a" widened to charT. 
+//     Otherwise inserts unsigned{wd} << " is not a valid weekday".
+// 
+// template<class charT, class traits>
+//   basic_ostream<charT, traits>&
+//   to_stream(basic_ostream<charT, traits>& os, const charT* fmt, const weekday& wd);
+// 
+//   Effects: Streams wd into os using the format specified by the NTCTS fmt. 
+//   fmt encoding follows the rules specified in 25.11.
+// 
+// template<class charT, class traits, class Alloc = allocator<charT>>
+//   basic_istream<charT, traits>&
+//   from_stream(basic_istream<charT, traits>& is, const charT* fmt,
+//             weekday& wd, basic_string<charT, traits, Alloc>* abbrev = nullptr,
+//             minutes* offset = nullptr);
+// 
+//   Effects: Attempts to parse the input stream is into the weekday wd using
+//       the format flags given in the NTCTS fmt as specified in 25.12.
+//     If the parse fails to decode a valid weekday, is.setstate(ios_- base::failbit)
+//       shall be called and wd shall not be modified.
+//     If %Z is used and successfully parsed, that value will be assigned
+//       to *abbrev if abbrev is non-null.
+//     If %z (or a modified variant) is used and successfully parsed,
+//       that value will be assigned to *offset if offset is non-null.
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+   using weekday = std::chrono::weekday;
+   
+   std::cout << weekday{3};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.weekday/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.weekday/types.pass.cpp
new file mode 100644
index 000000000..7fad10dc9
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.weekday/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class weekday;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using weekday = std::chrono::weekday;
+    
+    static_assert(std::is_trivially_copyable_v<weekday>, "");
+    static_assert(std::is_standard_layout_v<weekday>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/ctor.pass.cpp
new file mode 100644
index 000000000..615258910
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/ctor.pass.cpp
@@ -0,0 +1,46 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+//                     year() = default;
+//  explicit constexpr year(int m) noexcept;
+//  explicit constexpr operator int() const noexcept;
+
+//  Effects: Constructs an object of type year by initializing y_ with y.
+//    The value held is unspecified if d is not in the range [0, 255].
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year = std::chrono::year;
+
+    ASSERT_NOEXCEPT(year{});
+    ASSERT_NOEXCEPT(year(0U));
+    ASSERT_NOEXCEPT(static_cast<int>(year(0U)));
+    
+    constexpr year y0{};
+    static_assert(static_cast<int>(y0) == 0, "");
+
+    constexpr year y1{1};
+    static_assert(static_cast<int>(y1) == 1, "");
+    
+    for (int i = 0; i <= 2550; i += 7)
+    {
+        year year(i);
+        assert(static_cast<int>(year) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/decrement.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/decrement.pass.cpp
new file mode 100644
index 000000000..61d5617ed
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/decrement.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+//  constexpr year& operator--() noexcept;
+//  constexpr year operator--(int) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Y>
+constexpr bool testConstexpr()
+{
+    Y y1{10};
+    if (static_cast<int>(--y1) != 9) return false;
+    if (static_cast<int>(y1--) != 9) return false;
+    if (static_cast<int>(y1)   != 8) return false;
+    return true;
+}
+
+int main()
+{
+    using year = std::chrono::year;
+    ASSERT_NOEXCEPT(--(std::declval<year&>())  );
+    ASSERT_NOEXCEPT(  (std::declval<year&>())--);
+
+    ASSERT_SAME_TYPE(year , decltype(  std::declval<year&>()--));
+    ASSERT_SAME_TYPE(year&, decltype(--std::declval<year&>()  ));
+    
+    static_assert(testConstexpr<year>(), "");
+
+    for (int i = 11000; i <= 11020; ++i)
+    {
+        year year(i);
+        assert(static_cast<int>(--year) == i - 1);
+        assert(static_cast<int>(year--) == i - 1);
+        assert(static_cast<int>(year)   == i - 2);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/increment.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/increment.pass.cpp
new file mode 100644
index 000000000..ec21990c0
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/increment.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+//  constexpr year& operator++() noexcept;
+//  constexpr year operator++(int) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Y>
+constexpr bool testConstexpr()
+{
+    Y y1{10};
+    if (static_cast<int>(++y1) != 11) return false;
+    if (static_cast<int>(y1++) != 11) return false;
+    if (static_cast<int>(y1)   != 12) return false;
+    return true;
+}
+
+int main()
+{
+    using year = std::chrono::year;
+    ASSERT_NOEXCEPT(++(std::declval<year&>())  );
+    ASSERT_NOEXCEPT(  (std::declval<year&>())++);
+
+    ASSERT_SAME_TYPE(year , decltype(  std::declval<year&>()++));
+    ASSERT_SAME_TYPE(year&, decltype(++std::declval<year&>()  ));
+    
+    static_assert(testConstexpr<year>(), "");
+
+    for (int i = 11000; i <= 11020; ++i)
+    {
+        year year(i);
+        assert(static_cast<int>(++year) == i + 1);
+        assert(static_cast<int>(year++) == i + 1);
+        assert(static_cast<int>(year)   == i + 2);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/is_leap.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/is_leap.pass.cpp
new file mode 100644
index 000000000..2cd493a6f
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/is_leap.pass.cpp
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+// constexpr bool is_is_leap() const noexcept;
+//  y_ % 4 == 0 && (y_ % 100 != 0 || y_ % 400 == 0)
+//
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year = std::chrono::year;
+
+    ASSERT_NOEXCEPT(                year(1).is_leap());
+    ASSERT_SAME_TYPE(bool, decltype(year(1).is_leap()));
+
+    static_assert(!year{1}.is_leap(), "");
+    static_assert(!year{2}.is_leap(), "");
+    static_assert(!year{3}.is_leap(), "");
+    static_assert( year{4}.is_leap(), "");
+
+    assert( year{-2000}.is_leap());
+    assert( year{ -400}.is_leap());
+    assert(!year{ -300}.is_leap());
+    assert(!year{ -200}.is_leap());
+
+    assert(!year{  200}.is_leap());
+    assert(!year{  300}.is_leap());
+    assert( year{  400}.is_leap());
+    assert(!year{ 1997}.is_leap());
+    assert(!year{ 1998}.is_leap());
+    assert(!year{ 1999}.is_leap());
+    assert( year{ 2000}.is_leap());
+    assert(!year{ 2001}.is_leap());
+    assert(!year{ 2002}.is_leap());
+    assert(!year{ 2003}.is_leap());
+    assert( year{ 2004}.is_leap());
+    assert(!year{ 2100}.is_leap());
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/ok.pass.cpp
new file mode 100644
index 000000000..98a7dec5f
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/ok.pass.cpp
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+// constexpr bool ok() const noexcept;
+//  Returns: min() <= y_ && y_ <= max().
+//
+//  static constexpr year min() noexcept;
+//   Returns year{ 32767};
+//  static constexpr year max() noexcept;
+//   Returns year{-32767};
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year = std::chrono::year;
+
+    ASSERT_NOEXCEPT(                std::declval<const year>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const year>().ok()));
+
+    ASSERT_NOEXCEPT(                year::max());
+    ASSERT_SAME_TYPE(year, decltype(year::max()));
+
+    ASSERT_NOEXCEPT(                year::min());
+    ASSERT_SAME_TYPE(year, decltype(year::min()));
+
+    static_assert(static_cast<int>(year::min()) == -32767, "");
+    static_assert(static_cast<int>(year::max()) ==  32767, "");
+
+    assert(year{-20001}.ok());
+    assert(year{ -2000}.ok());
+    assert(year{    -1}.ok());
+    assert(year{     0}.ok());
+    assert(year{     1}.ok());
+    assert(year{  2000}.ok());
+    assert(year{ 20001}.ok());
+
+    static_assert(!year{-32768}.ok(), "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/plus_minus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/plus_minus.pass.cpp
new file mode 100644
index 000000000..9d96b3ffb
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/plus_minus.pass.cpp
@@ -0,0 +1,51 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+// constexpr year operator+() const noexcept;
+// constexpr year operator-() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Y>
+constexpr bool testConstexpr()
+{
+    Y y1{1};
+    if (static_cast<int>(+y1) !=  1) return false;
+    if (static_cast<int>(-y1) != -1) return false;
+    return true;
+}
+
+int main()
+{
+    using year  = std::chrono::year;
+    using years = std::chrono::years;
+
+    ASSERT_NOEXCEPT(+std::declval<year>());
+    ASSERT_NOEXCEPT(-std::declval<year>());
+
+    ASSERT_SAME_TYPE(year, decltype(+std::declval<year>()));
+    ASSERT_SAME_TYPE(year, decltype(-std::declval<year>()));
+    
+    static_assert(testConstexpr<year>(), "");
+
+    for (int i = 10000; i <= 10020; ++i)
+    {
+        year year(i);
+        assert(static_cast<int>(+year) ==  i);
+        assert(static_cast<int>(-year) == -i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/plus_minus_equal.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/plus_minus_equal.pass.cpp
new file mode 100644
index 000000000..0ebd2d668
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.members/plus_minus_equal.pass.cpp
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+// constexpr year& operator+=(const years& d) noexcept;
+// constexpr year& operator-=(const years& d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Y, typename Ys>
+constexpr bool testConstexpr()
+{
+    Y y1{1};
+    if (static_cast<int>(y1 += Ys{ 1}) !=  2) return false;
+    if (static_cast<int>(y1 += Ys{ 2}) !=  4) return false;
+    if (static_cast<int>(y1 += Ys{ 8}) != 12) return false;
+    if (static_cast<int>(y1 -= Ys{ 1}) != 11) return false;
+    if (static_cast<int>(y1 -= Ys{ 2}) !=  9) return false;
+    if (static_cast<int>(y1 -= Ys{ 8}) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using year  = std::chrono::year;
+    using years = std::chrono::years;
+
+    ASSERT_NOEXCEPT(std::declval<year&>() += std::declval<years>());
+    ASSERT_NOEXCEPT(std::declval<year&>() -= std::declval<years>());
+
+    ASSERT_SAME_TYPE(year&, decltype(std::declval<year&>() += std::declval<years>()));
+    ASSERT_SAME_TYPE(year&, decltype(std::declval<year&>() -= std::declval<years>()));
+    
+    static_assert(testConstexpr<year, years>(), "");
+
+    for (int i = 10000; i <= 10020; ++i)
+    {
+        year year(i);
+        assert(static_cast<int>(year += years{10}) == i + 10);
+        assert(static_cast<int>(year)              == i + 10);
+        assert(static_cast<int>(year -= years{ 9}) == i +  1);
+        assert(static_cast<int>(year)              == i +  1);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..a158c5e4b
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+// constexpr bool operator==(const year& x, const year& y) noexcept;
+// constexpr bool operator!=(const year& x, const year& y) noexcept;
+// constexpr bool operator< (const year& x, const year& y) noexcept;
+// constexpr bool operator> (const year& x, const year& y) noexcept;
+// constexpr bool operator<=(const year& x, const year& y) noexcept;
+// constexpr bool operator>=(const year& x, const year& y) noexcept;
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+
+int main()
+{
+    using year = std::chrono::year;
+
+    AssertComparisons6AreNoexcept<year>();
+    AssertComparisons6ReturnBool<year>();
+    
+    static_assert(testComparisons6Values<year>(0,0), "");
+    static_assert(testComparisons6Values<year>(0,1), "");
+    
+//  Some 'ok' values as well
+    static_assert(testComparisons6Values<year>( 5, 5), "");
+    static_assert(testComparisons6Values<year>( 5,10), "");
+    
+    for (int i = 1; i < 10; ++i)
+        for (int j = 1; j < 10; ++j)
+            assert(testComparisons6Values<year>(i, j));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/literals.fail.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/literals.fail.cpp
new file mode 100644
index 000000000..a8322bba1
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/literals.fail.cpp
@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-5, clang-6
+// UNSUPPORTED: apple-clang-6, apple-clang-7, apple-clang-8, apple-clang-9
+
+// <chrono>
+// class year;
+
+// constexpr year operator""y(unsigned long long y) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using std::chrono::year;
+    year d1 = 1234y; // expected-error-re {{no matching literal operator for call to 'operator""y' {{.*}}}}
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/literals.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/literals.pass.cpp
new file mode 100644
index 000000000..6ace29324
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/literals.pass.cpp
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-5, clang-6
+// UNSUPPORTED: apple-clang-6, apple-clang-7, apple-clang-8, apple-clang-9
+
+// <chrono>
+// class year;
+
+// constexpr year operator""y(unsigned long long y) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    {
+    using namespace std::chrono;
+    ASSERT_NOEXCEPT(4y);
+
+    static_assert( 2017y == year(2017), "");
+    year y1 = 2018y;
+    assert (y1 == year(2018));
+    }
+
+    {
+    using namespace std::literals;
+    ASSERT_NOEXCEPT(4d);
+
+    static_assert( 2017y == std::chrono::year(2017), "");
+
+    std::chrono::year y1 = 2020y;
+    assert (y1 == std::chrono::year(2020));
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/minus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/minus.pass.cpp
new file mode 100644
index 000000000..788b95896
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/minus.pass.cpp
@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+// constexpr year operator-(const year& x, const years& y) noexcept;
+//   Returns: x + -y.
+//
+// constexpr years operator-(const year& x, const year& y) noexcept;
+//   Returns: If x.ok() == true and y.ok() == true, returns a value m in the range 
+//   [years{0}, years{11}] satisfying y + m == x. 
+//   Otherwise the value returned is unspecified. 
+//   [Example: January - February == years{11}. —end example]
+
+extern "C" int printf(const char *, ...);
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Y, typename Ys>
+constexpr bool testConstexpr()
+{
+    Y y{2313};
+    Ys offset{1006};
+    if (y - offset != Y{1307}) return false;
+    if (y - Y{1307} != offset) return false;
+    return true;
+}
+
+int main()
+{
+    using year  = std::chrono::year;
+    using years = std::chrono::years;
+
+    ASSERT_NOEXCEPT(                 std::declval<year>() - std::declval<years>());
+    ASSERT_SAME_TYPE(year , decltype(std::declval<year>() - std::declval<years>()));
+
+    ASSERT_NOEXCEPT(                 std::declval<year>() - std::declval<year>());
+    ASSERT_SAME_TYPE(years, decltype(std::declval<year>() - std::declval<year>()));
+    
+    static_assert(testConstexpr<year, years>(), "");
+
+    year y{1223};
+    for (int i = 1100; i <= 1110; ++i)
+    {
+        year  y1 = y - years{i};
+        years ys1 = y - year{i};
+        assert(static_cast<int>(y1) == 1223 - i);
+        assert(ys1.count()          == 1223 - i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/plus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/plus.pass.cpp
new file mode 100644
index 000000000..9d71c953f
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/plus.pass.cpp
@@ -0,0 +1,59 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+// constexpr year operator+(const year& x, const years& y) noexcept;
+//   Returns: year(int{x} + y.count()).
+//
+// constexpr year operator+(const years& x, const year& y) noexcept;
+//   Returns: y + x
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename Y, typename Ys>
+constexpr bool testConstexpr()
+{
+    Y y{1001};
+    Ys offset{23};
+    if (y + offset != Y{1024}) return false;
+    if (offset + y != Y{1024}) return false;
+    return true;
+}
+
+int main()
+{
+    using year  = std::chrono::year;
+    using years = std::chrono::years;
+
+    ASSERT_NOEXCEPT(                std::declval<year>() + std::declval<years>());
+    ASSERT_SAME_TYPE(year, decltype(std::declval<year>() + std::declval<years>()));
+
+    ASSERT_NOEXCEPT(                std::declval<years>() + std::declval<year>());
+    ASSERT_SAME_TYPE(year, decltype(std::declval<years>() + std::declval<year>()));
+
+    static_assert(testConstexpr<year, years>(), "");
+
+    year y{1223};
+    for (int i = 1100; i <= 1110; ++i)
+    {
+        year y1 = y + years{i};
+        year y2 = years{i} + y;
+        assert(y1 == y2);
+        assert(static_cast<int>(y1) == i + 1223);
+        assert(static_cast<int>(y2) == i + 1223);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..120c2a15a
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/time.cal.year.nonmembers/streaming.pass.cpp
@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year;
+
+// template<class charT, class traits>
+//   basic_ostream<charT, traits>&
+//   operator<<(basic_ostream<charT, traits>& os, const year& y);
+// 
+//   Effects: Inserts format(fmt, y) where fmt is "%Y" widened to charT. 
+//   If !y.ok(), appends with " is not a valid year".
+// 
+// template<class charT, class traits>
+//   basic_ostream<charT, traits>&
+//   to_stream(basic_ostream<charT, traits>& os, const charT* fmt, const year& y);
+// 
+//   Effects: Streams y into os using the format specified by the NTCTS fmt. 
+//     fmt encoding follows the rules specified in 25.11.
+// 
+// template<class charT, class traits, class Alloc = allocator<charT>>
+//   basic_istream<charT, traits>&
+//   from_stream(basic_istream<charT, traits>& is, const charT* fmt,
+//               year& y, basic_string<charT, traits, Alloc>* abbrev = nullptr,
+//               minutes* offset = nullptr);
+// 
+//   Effects: Attempts to parse the input stream is into the year y using the format flags
+//     given in the NTCTS fmt as specified in 25.12. If the parse fails to decode a valid year,
+//     is.setstate(ios_base::failbit) shall be called and y shall not be modified. If %Z is used
+//     and successfully parsed, that value will be assigned to *abbrev if abbrev is non-null. 
+//     If %z (or a modified variant) is used and successfully parsed, that value will be 
+//     assigned to *offset if offset is non-null.
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+   using year = std::chrono::year;
+   
+   std::cout << year{2018};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.year/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.year/types.pass.cpp
new file mode 100644
index 000000000..24f2d773a
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.year/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year = std::chrono::year;
+    
+    static_assert(std::is_trivially_copyable_v<year>, "");
+    static_assert(std::is_standard_layout_v<year>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/ctor.pass.cpp
new file mode 100644
index 000000000..bfd1f531a
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/ctor.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+//            year_month() = default;
+//  constexpr year_month(const chrono::year& y, const chrono::month& m) noexcept;
+//
+//  Effects:  Constructs an object of type year_month by initializing y_ with y, and m_ with m.
+//
+//  constexpr chrono::year   year() const noexcept;
+//  constexpr chrono::month month() const noexcept;
+//  constexpr bool             ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year       = std::chrono::year;
+    using month      = std::chrono::month;
+    using year_month = std::chrono::year_month;
+
+    ASSERT_NOEXCEPT(year_month{});
+    ASSERT_NOEXCEPT(year_month{year{1}, month{1}});
+    
+    constexpr year_month ym0{};
+    static_assert( ym0.year()  == year{},  "");
+    static_assert( ym0.month() == month{}, "");
+    static_assert(!ym0.ok(),               "");
+
+    constexpr year_month ym1{year{2018}, std::chrono::January};
+    static_assert( ym1.year()  == year{2018},           "");
+    static_assert( ym1.month() == std::chrono::January, "");
+    static_assert( ym1.ok(),                            "");
+
+    constexpr year_month ym2{year{2018}, month{}};
+    static_assert( ym2.year()  == year{2018}, "");
+    static_assert( ym2.month() == month{},    "");
+    static_assert(!ym2.ok(),                  "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/month.pass.cpp
new file mode 100644
index 000000000..a747f52b6
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/month.pass.cpp
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+// constexpr chrono::month month() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year       = std::chrono::year;
+    using month      = std::chrono::month;
+    using year_month = std::chrono::year_month;
+
+    ASSERT_NOEXCEPT(                 std::declval<const year_month>().month());
+    ASSERT_SAME_TYPE(month, decltype(std::declval<const year_month>().month()));
+
+    static_assert( year_month{}.month() == month{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month ym(year{1234}, month{i});
+        assert( static_cast<unsigned>(ym.month()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/ok.pass.cpp
new file mode 100644
index 000000000..f6a9376e1
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/ok.pass.cpp
@@ -0,0 +1,50 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+// constexpr bool ok() const noexcept;
+//  Returns: m_.ok() && y_.ok().
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using month      = std::chrono::month;
+    using year       = std::chrono::year;
+    using year_month = std::chrono::year_month;
+
+    constexpr month January = std::chrono::January;
+
+    ASSERT_NOEXCEPT(                std::declval<const year_month>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const year_month>().ok()));
+
+    static_assert(!year_month{year{-32768}, January}.ok(), ""); // Bad year
+    static_assert(!year_month{year{2019},   month{}}.ok(), ""); // Bad month
+    static_assert( year_month{year{2019},   January}.ok(), ""); // Both OK
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        year_month ym{year{2019}, month{i}};
+        assert( ym.ok() == month{i}.ok());
+    }
+
+    const int ymax = static_cast<int>(year::max());
+    for (int i = ymax - 100; i <= ymax + 100; ++i)
+    {
+        year_month ym{year{i}, January};
+        assert( ym.ok() == year{i}.ok());
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/plus_minus_equal_month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/plus_minus_equal_month.pass.cpp
new file mode 100644
index 000000000..837eab769
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/plus_minus_equal_month.pass.cpp
@@ -0,0 +1,64 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+// constexpr year_month& operator+=(const months& d) noexcept;
+// constexpr year_month& operator-=(const months& d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr(D d1)
+{
+    if (static_cast<unsigned>((d1          ).month()) !=  1) return false;
+    if (static_cast<unsigned>((d1 += Ds{ 1}).month()) !=  2) return false;
+    if (static_cast<unsigned>((d1 += Ds{ 2}).month()) !=  4) return false;
+    if (static_cast<unsigned>((d1 += Ds{12}).month()) !=  4) return false;
+    if (static_cast<unsigned>((d1 -= Ds{ 1}).month()) !=  3) return false;
+    if (static_cast<unsigned>((d1 -= Ds{ 2}).month()) !=  1) return false;
+    if (static_cast<unsigned>((d1 -= Ds{12}).month()) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using month      = std::chrono::month;
+    using months     = std::chrono::months;
+    using year       = std::chrono::year;
+    using year_month = std::chrono::year_month;
+
+    ASSERT_NOEXCEPT(                       std::declval<year_month&>() += std::declval<months>());
+    ASSERT_SAME_TYPE(year_month&, decltype(std::declval<year_month&>() += std::declval<months>()));
+
+    ASSERT_NOEXCEPT(                       std::declval<year_month&>() -= std::declval<months>());
+    ASSERT_SAME_TYPE(year_month&, decltype(std::declval<year_month&>() -= std::declval<months>()));
+    
+    static_assert(testConstexpr<year_month, months>(year_month{year{1234}, month{1}}), "");
+
+    for (unsigned i = 0; i <= 10; ++i)
+    {
+        year y{1234};
+        year_month ym(y, month{i});
+        assert(static_cast<unsigned>((ym += months{2}).month()) == i + 2);
+        assert(ym.year() == y);
+        assert(static_cast<unsigned>((ym             ).month()) == i + 2);
+        assert(ym.year() == y);
+        assert(static_cast<unsigned>((ym -= months{1}).month()) == i + 1);
+        assert(ym.year() == y);
+        assert(static_cast<unsigned>((ym             ).month()) == i + 1);
+        assert(ym.year() == y);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/plus_minus_equal_year.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/plus_minus_equal_year.pass.cpp
new file mode 100644
index 000000000..f5d8e327e
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/plus_minus_equal_year.pass.cpp
@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+// constexpr year_month& operator+=(const years& d) noexcept;
+// constexpr year_month& operator-=(const years& d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr(D d1)
+{
+    if (static_cast<int>((d1          ).year()) !=  1) return false;
+    if (static_cast<int>((d1 += Ds{ 1}).year()) !=  2) return false;
+    if (static_cast<int>((d1 += Ds{ 2}).year()) !=  4) return false;
+    if (static_cast<int>((d1 += Ds{12}).year()) != 16) return false;
+    if (static_cast<int>((d1 -= Ds{ 1}).year()) != 15) return false;
+    if (static_cast<int>((d1 -= Ds{ 2}).year()) != 13) return false;
+    if (static_cast<int>((d1 -= Ds{12}).year()) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using month      = std::chrono::month;
+    using year       = std::chrono::year;
+    using years      = std::chrono::years;
+    using year_month = std::chrono::year_month;
+
+
+    ASSERT_NOEXCEPT(                       std::declval<year_month&>() += std::declval<years>());
+    ASSERT_SAME_TYPE(year_month&, decltype(std::declval<year_month&>() += std::declval<years>()));
+
+    ASSERT_NOEXCEPT(                       std::declval<year_month&>() -= std::declval<years>());
+    ASSERT_SAME_TYPE(year_month&, decltype(std::declval<year_month&>() -= std::declval<years>()));
+    
+    static_assert(testConstexpr<year_month, years>(year_month{year{1}, month{1}}), "");
+
+    for (int i = 1000; i <= 1010; ++i)
+    {
+        month m{2};
+        year_month ym(year{i}, m);
+        assert(static_cast<int>((ym += years{2}).year()) == i + 2);
+        assert(ym.month() == m);
+        assert(static_cast<int>((ym            ).year()) == i + 2);
+        assert(ym.month() == m);
+        assert(static_cast<int>((ym -= years{1}).year()) == i + 1);
+        assert(ym.month() == m);
+        assert(static_cast<int>((ym            ).year()) == i + 1);
+        assert(ym.month() == m);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/year.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/year.pass.cpp
new file mode 100644
index 000000000..96fda2796
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.members/year.pass.cpp
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+// constexpr chrono::day day() const noexcept;
+//  Returns: d_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year       = std::chrono::year;
+    using month      = std::chrono::month;
+    using year_month = std::chrono::year_month;
+
+    ASSERT_NOEXCEPT(                std::declval<const year_month>().year());
+    ASSERT_SAME_TYPE(year, decltype(std::declval<const year_month>().year()));
+
+    static_assert( year_month{}.year() == year{}, "");
+
+    for (int i = 1; i <= 50; ++i)
+    {
+        year_month ym(year{i}, month{});
+        assert( static_cast<int>(ym.year()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..9761078b2
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,69 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+// constexpr bool operator==(const year_month& x, const year_month& y) noexcept;
+//   Returns: x.year() == y.year() && x.month() == y.month().
+//
+// constexpr bool operator< (const year_month& x, const year_month& y) noexcept;
+//   Returns: 
+//      If x.year() < y.year() returns true. 
+//      Otherwise, if x.year() > y.year() returns false. 
+//      Otherwise, returns x.month() < y.month().
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using year       = std::chrono::year;
+    using month      = std::chrono::month;
+    using year_month = std::chrono::year_month;
+
+    AssertComparisons6AreNoexcept<year_month>();
+    AssertComparisons6ReturnBool<year_month>();
+    
+    static_assert( testComparisons6(
+        year_month{year{1234}, std::chrono::January}, 
+        year_month{year{1234}, std::chrono::January},
+        true, false), "");
+    
+    static_assert( testComparisons6(
+        year_month{year{1234}, std::chrono::January}, 
+        year_month{year{1234}, std::chrono::February},
+        false, true), "");
+
+    static_assert( testComparisons6(
+        year_month{year{1234}, std::chrono::January}, 
+        year_month{year{1235}, std::chrono::January},
+        false, true), "");
+
+//  same year, different months
+    for (unsigned i = 1; i < 12; ++i)
+        for (unsigned j = 1; j < 12; ++j)
+            assert((testComparisons6(
+                year_month{year{1234}, month{i}}, 
+                year_month{year{1234}, month{j}}, 
+                i == j, i < j )));
+    
+//  same month, different years
+    for (int i = 1000; i < 20; ++i)
+        for (int j = 1000; j < 20; ++j)
+        assert((testComparisons6(
+            year_month{year{i}, std::chrono::January}, 
+            year_month{year{j}, std::chrono::January},
+            i == j, i < j )));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/minus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/minus.pass.cpp
new file mode 100644
index 000000000..e443c50e7
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/minus.pass.cpp
@@ -0,0 +1,90 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+// constexpr year_month operator-(const year_month& ym, const years& dy) noexcept;
+// Returns: ym + -dy.                
+// 
+// constexpr year_month operator-(const year_month& ym, const months& dm) noexcept;
+// Returns: ym + -dm.
+// 
+// constexpr months operator-(const year_month& x, const year_month& y) noexcept;
+// Returns: x.year() - y.year() + months{static_cast<int>(unsigned{x.month()}) -
+//                                       static_cast<int>(unsigned{y.month()})}
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+#include <iostream>
+
+int main()
+{
+    using year       = std::chrono::year;
+    using years      = std::chrono::years;
+    using month      = std::chrono::month;
+    using months     = std::chrono::months;
+    using year_month = std::chrono::year_month;
+
+    {   // year_month - years
+    ASSERT_NOEXCEPT(                      std::declval<year_month>() - std::declval<years>());
+    ASSERT_SAME_TYPE(year_month, decltype(std::declval<year_month>() - std::declval<years>()));
+    
+//  static_assert(testConstexprYears (year_month{year{1}, month{1}}), "");
+
+    year_month ym{year{1234}, std::chrono::January};
+    for (int i = 0; i <= 10; ++i)
+    {
+        year_month ym1 = ym - years{i};
+        assert(static_cast<int>(ym1.year()) == 1234 - i);
+        assert(ym1.month() == std::chrono::January);
+    }
+    }
+
+    {   // year_month - months
+    ASSERT_NOEXCEPT(                      std::declval<year_month>() - std::declval<months>());
+    ASSERT_SAME_TYPE(year_month, decltype(std::declval<year_month>() - std::declval<months>()));
+    
+//  static_assert(testConstexprMonths(year_month{year{1}, month{1}}), "");
+
+    year_month ym{year{1234}, std::chrono::November};
+    for (int i = 0; i <= 10; ++i)  // TODO test wrap-around
+    {
+        year_month ym1 = ym - months{i};
+        assert(static_cast<int>(ym1.year()) == 1234);
+        assert(ym1.month() == month(11 - i));
+    }
+    }
+
+    {   // year_month - year_month
+    ASSERT_NOEXCEPT(                  std::declval<year_month>() - std::declval<year_month>());
+    ASSERT_SAME_TYPE(months, decltype(std::declval<year_month>() - std::declval<year_month>()));
+    
+//  static_assert(testConstexprMonths(year_month{year{1}, month{1}}), "");
+
+//  Same year
+    year y{2345};
+    for (int i = 1; i <= 12; ++i)
+        for (int j = 1; j <= 12; ++j)
+    {
+        months diff = year_month{y, month(i)} - year_month{y, month(j)};
+        std::cout << "i: " << i << " j: " << j << " -> " << diff.count() << std::endl;
+        assert(diff.count() == i - j);
+    }
+
+//  TODO: different year
+
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/plus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/plus.pass.cpp
new file mode 100644
index 000000000..acf93ef18
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/plus.pass.cpp
@@ -0,0 +1,106 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+// constexpr year_month operator+(const year_month& ym, const years& dy) noexcept;
+// Returns: (ym.year() + dy) / ym.month().
+// 
+// constexpr year_month operator+(const years& dy, const year_month& ym) noexcept;
+// Returns: ym + dy.
+//
+// constexpr year_month operator+(const year_month& ym, const months& dm) noexcept;
+// Returns: A year_month value z such that z - ym == dm. 
+// Complexity: O(1) with respect to the value of dm.
+// 
+// constexpr year_month operator+(const months& dm, const year_month& ym) noexcept;
+// Returns: ym + dm.
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool testConstexprYears(std::chrono::year_month ym)
+{
+    std::chrono::years offset{23};
+    if (static_cast<int>((ym         ).year()) !=  1) return false;
+    if (static_cast<int>((ym + offset).year()) != 24) return false;
+    if (static_cast<int>((offset + ym).year()) != 24) return false;
+    return true;
+}
+
+
+constexpr bool testConstexprMonths(std::chrono::year_month ym)
+{
+    std::chrono::months offset{6};
+    if (static_cast<unsigned>((ym         ).month()) !=  1) return false;
+    if (static_cast<unsigned>((ym + offset).month()) !=  7) return false;
+    if (static_cast<unsigned>((offset + ym).month()) !=  7) return false;
+    return true;
+}
+
+
+int main()
+{
+    using year       = std::chrono::year;
+    using years      = std::chrono::years;
+    using month      = std::chrono::month;
+    using months     = std::chrono::months;
+    using year_month = std::chrono::year_month;
+
+    {   // year_month + years
+    ASSERT_NOEXCEPT(std::declval<year_month>() + std::declval<years>());
+    ASSERT_NOEXCEPT(std::declval<years>() + std::declval<year_month>());
+
+    ASSERT_SAME_TYPE(year_month, decltype(std::declval<year_month>() + std::declval<years>()));
+    ASSERT_SAME_TYPE(year_month, decltype(std::declval<years>() + std::declval<year_month>()));
+    
+    static_assert(testConstexprYears (year_month{year{1}, month{1}}), "");
+
+    year_month ym{year{1234}, std::chrono::January};
+    for (int i = 0; i <= 10; ++i)
+    {
+        year_month ym1 = ym + years{i};
+        year_month ym2 = years{i} + ym;
+        assert(static_cast<int>(ym1.year()) == i + 1234);
+        assert(static_cast<int>(ym2.year()) == i + 1234);
+        assert(ym1.month() == std::chrono::January);
+        assert(ym2.month() == std::chrono::January);
+        assert(ym1 == ym2);
+    }
+    }
+
+    {   // year_month + months
+    ASSERT_NOEXCEPT(std::declval<year_month>() + std::declval<months>());
+    ASSERT_NOEXCEPT(std::declval<months>() + std::declval<year_month>());
+
+    ASSERT_SAME_TYPE(year_month, decltype(std::declval<year_month>() + std::declval<months>()));
+    ASSERT_SAME_TYPE(year_month, decltype(std::declval<months>() + std::declval<year_month>()));
+
+    static_assert(testConstexprMonths(year_month{year{1}, month{1}}), "");
+
+    year_month ym{year{1234}, std::chrono::January};
+    for (int i = 0; i <= 10; ++i)  // TODO test wrap-around
+    {
+        year_month ym1 = ym + months{i};
+        year_month ym2 = months{i} + ym;
+        assert(static_cast<int>(ym1.year()) == 1234);
+        assert(static_cast<int>(ym2.year()) == 1234);
+        assert(ym1.month() == month(1 + i));
+        assert(ym2.month() == month(1 + i));
+        assert(ym1 == ym2);
+    }
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..2a94d4ffd
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/time.cal.ym.nonmembers/streaming.pass.cpp
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month;
+
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const year_month& ym);
+// 
+// Returns: os << ym.year() << '/' << ym.month().
+// 
+// 
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     to_stream(basic_ostream<charT, traits>& os, const charT* fmt, const year_month& ym);
+// 
+// Effects: Streams ym into os using the format specified by the NTCTS fmt. fmt encoding follows the rules specified in 25.11.
+// 
+// template<class charT, class traits, class Alloc = allocator<charT>>
+//     basic_istream<charT, traits>&
+//   from_stream(basic_istream<charT, traits>& is, const charT* fmt,
+//               year_month& ym, basic_string<charT, traits, Alloc>* abbrev = nullptr,
+//               minutes* offset = nullptr);
+// 
+// Effects: Attempts to parse the input stream is into the year_month ym using the format 
+//         flags given in the NTCTS fmt as specified in 25.12. If the parse fails to decode
+//         a valid year_month, is.setstate(ios_- base::failbit) shall be called and ym shall
+//         not be modified. If %Z is used and successfully parsed, that value will be assigned
+//         to *abbrev if abbrev is non-null. If %z (or a modified variant) is used and 
+//         successfully parsed, that value will be assigned to *offset if offset is non-null.
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year_month = std::chrono::year_month;
+    using year       = std::chrono::year;
+    using month      = std::chrono::month;
+    
+    std::cout << year_month{year{2018}, month{3}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ym/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ym/types.pass.cpp
new file mode 100644
index 000000000..c888dd5fe
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ym/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year_month = std::chrono::year_month;
+    
+    static_assert(std::is_trivially_copyable_v<year_month>, "");
+    static_assert(std::is_standard_layout_v<year_month>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.local_days.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.local_days.pass.cpp
new file mode 100644
index 000000000..c95ba36aa
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.local_days.pass.cpp
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_day;
+
+//  explicit constexpr year_month_day(const local_days& dp) noexcept;
+//
+//
+//  Effects:  Constructs an object of type year_month_day that corresponds 
+//                to the date represented by dp
+//
+//  Remarks: Equivalent to constructing with sys_days{dp.time_since_epoch()}.
+//
+//  constexpr chrono::year   year() const noexcept;
+//  constexpr chrono::month month() const noexcept;
+//  constexpr chrono::day     day() const noexcept;
+//  constexpr bool             ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+//  using local_days     = std::chrono::local_days;
+    using year_month_day = std::chrono::year_month_day;
+
+//  ASSERT_NOEXCEPT(year_month_day{std::declval<const local_days>()});
+    assert(false);
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.pass.cpp
new file mode 100644
index 000000000..dd2b1e133
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.pass.cpp
@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+//  year_month_day() = default;
+//  constexpr year_month_day(const chrono::year& y, const chrono::month& m,
+//                                   const chrono::day& d) noexcept;
+//
+//  Effects:  Constructs an object of type year_month_day by initializing
+//                y_ with y, m_ with m, and d_ with d.
+//
+//  constexpr chrono::year   year() const noexcept;
+//  constexpr chrono::month month() const noexcept;
+//  constexpr chrono::day     day() const noexcept;
+//  constexpr bool             ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+    using year_month_day = std::chrono::year_month_day;
+
+    ASSERT_NOEXCEPT(year_month_day{});
+    ASSERT_NOEXCEPT(year_month_day{year{1}, month{1}, day{1}});
+    
+    constexpr month January = std::chrono::January;
+    
+    constexpr year_month_day ym0{};
+    static_assert( ym0.year()  == year{},  "");
+    static_assert( ym0.month() == month{}, "");
+    static_assert( ym0.day()   == day{},   "");
+    static_assert(!ym0.ok(),               "");
+
+    constexpr year_month_day ym1{year{2019}, January, day{12}};
+    static_assert( ym1.year()  == year{2019}, "");
+    static_assert( ym1.month() == January,    "");
+    static_assert( ym1.day()   == day{12},    "");
+    static_assert( ym1.ok(),                  "");
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.sys_days.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.sys_days.pass.cpp
new file mode 100644
index 000000000..38c9d68ea
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.sys_days.pass.cpp
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_day;
+
+//  constexpr year_month_day(const sys_days& dp) noexcept;
+//
+//  Effects:  Constructs an object of type year_month_day that corresponds 
+//                to the date represented by dp
+//
+//  Remarks: For any value ymd of type year_month_day for which ymd.ok() is true, 
+//                ymd == year_month_day{sys_days{ymd}} is true.
+//
+//  constexpr chrono::year   year() const noexcept;
+//  constexpr chrono::month month() const noexcept;
+//  constexpr bool             ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+//  using sys_days     = std::chrono::sys_days;
+    using year_month_day = std::chrono::year_month_day;
+
+//  ASSERT_NOEXCEPT(year_month_day{std::declval<const sys_days>()});
+    assert(false);
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.year_month_day_last.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.year_month_day_last.pass.cpp
new file mode 100644
index 000000000..e1211c076
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ctor.year_month_day_last.pass.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_day;
+
+//  constexpr year_month_day(const year_month_day_last& ymdl) noexcept;
+//
+//  Effects:  Constructs an object of type year_month_day by initializing
+//              y_ with ymdl.year(), m_ with ymdl.month(), and d_ with ymdl.day().
+//
+//  constexpr chrono::year   year() const noexcept;
+//  constexpr chrono::month month() const noexcept;
+//  constexpr chrono::day     day() const noexcept;
+//  constexpr bool             ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+//  using year_month_day_last = std::chrono::year_month_day_last;
+    using year_month_day      = std::chrono::year_month_day;
+
+//  ASSERT_NOEXCEPT(year_month_day{std::declval<const year_month_day_last>()});
+    assert(false);
+    
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/day.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/day.pass.cpp
new file mode 100644
index 000000000..603a01676
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/day.pass.cpp
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+// constexpr chrono::day day() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+    using year_month_day = std::chrono::year_month_day;
+
+    ASSERT_NOEXCEPT(               std::declval<const year_month_day>().day());
+    ASSERT_SAME_TYPE(day, decltype(std::declval<const year_month_day>().day()));
+
+    static_assert( year_month_day{}.day() == day{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month_day ymd(year{1234}, month{2}, day{i});
+        assert( static_cast<unsigned>(ymd.day()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/month.pass.cpp
new file mode 100644
index 000000000..40dd733cf
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/month.pass.cpp
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+// constexpr chrono::month month() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+    using year_month_day = std::chrono::year_month_day;
+
+    ASSERT_NOEXCEPT(                 std::declval<const year_month_day>().month());
+    ASSERT_SAME_TYPE(month, decltype(std::declval<const year_month_day>().month()));
+
+    static_assert( year_month_day{}.month() == month{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month_day ymd(year{1234}, month{i}, day{12});
+        assert( static_cast<unsigned>(ymd.month()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ok.pass.cpp
new file mode 100644
index 000000000..c5c6e3e70
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/ok.pass.cpp
@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+// constexpr bool ok() const noexcept;
+//  Returns: m_.ok() && y_.ok().
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+    using year_month_day = std::chrono::year_month_day;
+
+    constexpr month January = std::chrono::January;
+
+    ASSERT_NOEXCEPT(                std::declval<const year_month_day>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const year_month_day>().ok()));
+
+    static_assert(!year_month_day{year{-32768}, month{}, day{}}.ok(), ""); // All three bad
+
+    static_assert(!year_month_day{year{-32768}, January, day{1}}.ok(), ""); // Bad year
+    static_assert(!year_month_day{year{2019},   month{}, day{1}}.ok(), ""); // Bad month
+    static_assert(!year_month_day{year{2019},   January, day{} }.ok(), ""); // Bad day
+
+    static_assert(!year_month_day{year{-32768}, month{}, day{1}}.ok(), ""); // Bad year & month
+    static_assert(!year_month_day{year{2019},   month{}, day{} }.ok(), ""); // Bad month & day
+    static_assert(!year_month_day{year{-32768}, January, day{} }.ok(), ""); // Bad year & day
+
+    static_assert( year_month_day{year{2019},   January, day{1}}.ok(), ""); // All OK
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        year_month_day ym{year{2019}, January, day{i}};
+        assert( ym.ok() == day{i}.ok());
+    }
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        year_month_day ym{year{2019}, month{i}, day{12}};
+        assert( ym.ok() == month{i}.ok());
+    }
+
+    const int ymax = static_cast<int>(year::max());
+    for (int i = ymax - 100; i <= ymax + 100; ++i)
+    {
+        year_month_day ym{year{i}, January, day{12}};
+        assert( ym.ok() == year{i}.ok());
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/plus_minus_equal_month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/plus_minus_equal_month.pass.cpp
new file mode 100644
index 000000000..2249d91f9
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/plus_minus_equal_month.pass.cpp
@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+// constexpr year_month_day& operator+=(const months& m) noexcept;
+// constexpr year_month_day& operator-=(const months& m) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr(D d1)
+{
+    if (static_cast<unsigned>((d1          ).month()) !=  1) return false;
+    if (static_cast<unsigned>((d1 += Ds{ 1}).month()) !=  2) return false;
+    if (static_cast<unsigned>((d1 += Ds{ 2}).month()) !=  4) return false;
+    if (static_cast<unsigned>((d1 += Ds{12}).month()) !=  4) return false;
+    if (static_cast<unsigned>((d1 -= Ds{ 1}).month()) !=  3) return false;
+    if (static_cast<unsigned>((d1 -= Ds{ 2}).month()) !=  1) return false;
+    if (static_cast<unsigned>((d1 -= Ds{12}).month()) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+    using year_month_day = std::chrono::year_month_day;
+    using months         = std::chrono::months;
+
+    ASSERT_NOEXCEPT(std::declval<year_month_day&>() += std::declval<months>());
+    ASSERT_NOEXCEPT(std::declval<year_month_day&>() -= std::declval<months>());
+
+    ASSERT_SAME_TYPE(year_month_day&, decltype(std::declval<year_month_day&>() += std::declval<months>()));
+    ASSERT_SAME_TYPE(year_month_day&, decltype(std::declval<year_month_day&>() -= std::declval<months>()));
+    
+    static_assert(testConstexpr<year_month_day, months>(year_month_day{year{1234}, month{1}, day{1}}), "");
+
+    for (unsigned i = 0; i <= 10; ++i)
+    {
+        year y{1234};
+        day   d{23};
+        year_month_day ym(y, month{i}, d);
+        assert(static_cast<unsigned>((ym += months{2}).month()) == i + 2);
+        assert(ym.year() == y);
+        assert(ym.day()  == d);
+        assert(static_cast<unsigned>((ym             ).month()) == i + 2);
+        assert(ym.year() == y);
+        assert(ym.day()  == d);
+        assert(static_cast<unsigned>((ym -= months{1}).month()) == i + 1);
+        assert(ym.year() == y);
+        assert(ym.day()  == d);
+        assert(static_cast<unsigned>((ym             ).month()) == i + 1);
+        assert(ym.year() == y);
+        assert(ym.day()  == d);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/plus_minus_equal_year.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/plus_minus_equal_year.pass.cpp
new file mode 100644
index 000000000..f9973c105
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/plus_minus_equal_year.pass.cpp
@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+// constexpr year_month_day& operator+=(const years& d) noexcept;
+// constexpr year_month_day& operator-=(const years& d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr(D d1)
+{
+    if (static_cast<int>((d1          ).year()) !=  1) return false;
+    if (static_cast<int>((d1 += Ds{ 1}).year()) !=  2) return false;
+    if (static_cast<int>((d1 += Ds{ 2}).year()) !=  4) return false;
+    if (static_cast<int>((d1 += Ds{12}).year()) != 16) return false;
+    if (static_cast<int>((d1 -= Ds{ 1}).year()) != 15) return false;
+    if (static_cast<int>((d1 -= Ds{ 2}).year()) != 13) return false;
+    if (static_cast<int>((d1 -= Ds{12}).year()) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+    using year_month_day = std::chrono::year_month_day;
+    using years          = std::chrono::years;
+
+    ASSERT_NOEXCEPT(std::declval<year_month_day&>() += std::declval<years>());
+    ASSERT_NOEXCEPT(std::declval<year_month_day&>() -= std::declval<years>());
+
+    ASSERT_SAME_TYPE(year_month_day&, decltype(std::declval<year_month_day&>() += std::declval<years>()));
+    ASSERT_SAME_TYPE(year_month_day&, decltype(std::declval<year_month_day&>() -= std::declval<years>()));
+    
+    static_assert(testConstexpr<year_month_day, years>(year_month_day{year{1}, month{1}, day{1}}), "");
+
+    for (int i = 1000; i <= 1010; ++i)
+    {
+        month m{2};
+        day   d{23};
+        year_month_day ym(year{i}, m, d);
+        assert(static_cast<int>((ym += years{2}).year()) == i + 2);
+        assert(ym.month() == m);
+        assert(ym.day()   == d);
+        assert(static_cast<int>((ym            ).year()) == i + 2);
+        assert(ym.month() == m);
+        assert(ym.day()   == d);
+        assert(static_cast<int>((ym -= years{1}).year()) == i + 1);
+        assert(ym.month() == m);
+        assert(ym.day()   == d);
+        assert(static_cast<int>((ym            ).year()) == i + 1);
+        assert(ym.month() == m);
+        assert(ym.day()   == d);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/year.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/year.pass.cpp
new file mode 100644
index 000000000..54dbd832c
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.members/year.pass.cpp
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+// constexpr chrono::day day() const noexcept;
+//  Returns: d_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+    using year_month_day = std::chrono::year_month_day;
+
+    ASSERT_NOEXCEPT(                std::declval<const year_month_day>().year());
+    ASSERT_SAME_TYPE(year, decltype(std::declval<const year_month_day>().year()));
+
+    static_assert( year_month_day{}.year() == year{}, "");
+
+    for (int i = 1; i <= 50; ++i)
+    {
+        year_month_day ym(year{i}, month{}, day{});
+        assert( static_cast<int>(ym.year()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..e686d9a42
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,118 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+// constexpr bool operator==(const year_month_day& x, const year_month_day& y) noexcept;
+//   Returns: x.year() == y.year() && x.month() == y.month().
+//
+// constexpr bool operator< (const year_month_day& x, const year_month_day& y) noexcept;
+//   Returns: 
+//      If x.year() < y.year() returns true. 
+//      Otherwise, if x.year() > y.year() returns false. 
+//      Otherwise, if x.month() < y.month() returns true.
+//      Otherwise, if x.month() > y.month() returns false.
+//      Otherwise, returns x.day() < y.day()
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using day        = std::chrono::day;
+    using year       = std::chrono::year;
+    using month      = std::chrono::month;
+    using year_month_day = std::chrono::year_month_day;
+
+    AssertComparisons6AreNoexcept<year_month_day>();
+    AssertComparisons6ReturnBool<year_month_day>();
+    
+    constexpr month January = std::chrono::January;
+    constexpr month February = std::chrono::February;
+
+    static_assert( testComparisons6(
+        year_month_day{year{1234}, January, day{1}}, 
+        year_month_day{year{1234}, January, day{1}},
+        true, false), "");
+    
+//  different day
+    static_assert( testComparisons6(
+        year_month_day{year{1234}, January, day{1}}, 
+        year_month_day{year{1234}, January, day{2}},
+        false, true), "");
+    
+//  different month
+    static_assert( testComparisons6(
+        year_month_day{year{1234}, January, day{1}},
+        year_month_day{year{1234}, February, day{1}},
+        false, true), "");
+
+//  different year
+    static_assert( testComparisons6(
+        year_month_day{year{1234}, January, day{1}},
+        year_month_day{year{1235}, January, day{1}},
+        false, true), "");
+
+
+//  different month and day
+    static_assert( testComparisons6(
+        year_month_day{year{1234}, January, day{2}},
+        year_month_day{year{1234}, February, day{1}},
+        false, true), "");
+
+//  different year and month
+    static_assert( testComparisons6(
+        year_month_day{year{1234}, February, day{1}},
+        year_month_day{year{1235}, January, day{1}},
+        false, true), "");
+
+//  different year and day
+    static_assert( testComparisons6(
+        year_month_day{year{1234}, January, day{2}},
+        year_month_day{year{1235}, January, day{1}},
+        false, true), "");
+
+//  different year, month and day
+    static_assert( testComparisons6(
+        year_month_day{year{1234}, February, day{2}},
+        year_month_day{year{1235}, January, day{1}},
+        false, true), "");
+
+
+//  same year, different days
+    for (unsigned i = 1; i < 28; ++i)
+        for (unsigned j = 1; j < 28; ++j)
+            assert((testComparisons6(
+                year_month_day{year{1234}, January, day{i}}, 
+                year_month_day{year{1234}, January, day{j}}, 
+                i == j, i < j )));
+    
+//  same year, different months
+    for (unsigned i = 1; i < 12; ++i)
+        for (unsigned j = 1; j < 12; ++j)
+            assert((testComparisons6(
+                year_month_day{year{1234}, month{i}, day{12}}, 
+                year_month_day{year{1234}, month{j}, day{12}}, 
+                i == j, i < j )));
+    
+//  same month, different years
+    for (int i = 1000; i < 20; ++i)
+        for (int j = 1000; j < 20; ++j)
+        assert((testComparisons6(
+            year_month_day{year{i}, January, day{12}}, 
+            year_month_day{year{j}, January, day{12}},
+            i == j, i < j )));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/minus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/minus.pass.cpp
new file mode 100644
index 000000000..3f6012043
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/minus.pass.cpp
@@ -0,0 +1,60 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+// constexpr year_month_day operator-(const year_month_day& ymd, const years& dy) noexcept;
+//    Returns: ymd + (-dy)          
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+#include <iostream>
+
+constexpr bool test_constexpr ()
+{
+    std::chrono::year_month_day ym0{std::chrono::year{1234}, std::chrono::January, std::chrono::day{12}};
+    std::chrono::year_month_day ym1 = ym0 - std::chrono::years{10};
+    return
+        ym1.year()  == std::chrono::year{1234-10}
+     && ym1.month() == std::chrono::January
+     && ym1.day()   == std::chrono::day{12}
+        ;
+}
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+    using year_month_day = std::chrono::year_month_day;
+    using years          = std::chrono::years;
+
+    ASSERT_NOEXCEPT(                          std::declval<year_month_day>() - std::declval<years>());
+    ASSERT_SAME_TYPE(year_month_day, decltype(std::declval<year_month_day>() - std::declval<years>()));
+
+    constexpr month January = std::chrono::January;
+
+    static_assert(test_constexpr(), "");
+    
+    year_month_day ym{year{1234}, January, day{10}};
+    for (int i = 0; i <= 10; ++i)
+    {
+        year_month_day ym1 = ym - years{i};
+        assert(static_cast<int>(ym1.year()) == 1234 - i);
+        assert(ym1.month() == January);
+        assert(ym1.day() == day{10});
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/plus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/plus.pass.cpp
new file mode 100644
index 000000000..bc7649d94
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/plus.pass.cpp
@@ -0,0 +1,112 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+// constexpr year_month_day operator+(const year_month_day& ymd, const months& dm) noexcept;
+//   Returns: (ymd.year() / ymd.month() + dm) / ymd.day().
+// 
+// constexpr year_month_day operator+(const months& dm, const year_month_day& ymd) noexcept;
+//   Returns: ymd + dm.
+//
+//
+// constexpr year_month_day operator+(const year_month_day& ymd, const years& dy) noexcept;
+//   Returns: (ymd.year() + dy) / ymd.month() / ymd.day().
+// 
+// constexpr year_month_day operator+(const years& dy, const year_month_day& ymd) noexcept;
+//   Returns: ym + dm.
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool testConstexprYears(std::chrono::year_month_day ym)
+{
+    std::chrono::years offset{23};
+    if (static_cast<int>((ym         ).year()) !=  1) return false;
+    if (static_cast<int>((ym + offset).year()) != 24) return false;
+    if (static_cast<int>((offset + ym).year()) != 24) return false;
+    return true;
+}
+
+
+constexpr bool testConstexprMonths(std::chrono::year_month_day ym)
+{
+    std::chrono::months offset{6};
+    if (static_cast<unsigned>((ym         ).month()) !=  1) return false;
+    if (static_cast<unsigned>((ym + offset).month()) !=  7) return false;
+    if (static_cast<unsigned>((offset + ym).month()) !=  7) return false;
+    return true;
+}
+
+
+int main()
+{
+    using day        = std::chrono::day;
+    using year       = std::chrono::year;
+    using years      = std::chrono::years;
+    using month      = std::chrono::month;
+    using months     = std::chrono::months;
+    using year_month_day = std::chrono::year_month_day;
+
+    {   // year_month_day + months
+    ASSERT_NOEXCEPT(std::declval<year_month_day>() + std::declval<months>());
+    ASSERT_NOEXCEPT(std::declval<months>() + std::declval<year_month_day>());
+
+    ASSERT_SAME_TYPE(year_month_day, decltype(std::declval<year_month_day>() + std::declval<months>()));
+    ASSERT_SAME_TYPE(year_month_day, decltype(std::declval<months>() + std::declval<year_month_day>()));
+
+    static_assert(testConstexprMonths(year_month_day{year{1}, month{1}, day{1}}), "");
+
+    year_month_day ym{year{1234}, std::chrono::January, day{12}};
+    for (int i = 0; i <= 10; ++i)  // TODO test wrap-around
+    {
+        year_month_day ym1 = ym + months{i};
+        year_month_day ym2 = months{i} + ym;
+        assert(static_cast<int>(ym1.year()) == 1234);
+        assert(static_cast<int>(ym2.year()) == 1234);
+        assert(ym1.month() == month(1 + i));
+        assert(ym2.month() == month(1 + i));
+        assert(ym1.day()   == day{12});
+        assert(ym2.day()   == day{12});
+        assert(ym1 == ym2);
+    }
+    }
+
+    {   // year_month_day + years
+    ASSERT_NOEXCEPT(std::declval<year_month_day>() + std::declval<years>());
+    ASSERT_NOEXCEPT(std::declval<years>() + std::declval<year_month_day>());
+
+    ASSERT_SAME_TYPE(year_month_day, decltype(std::declval<year_month_day>() + std::declval<years>()));
+    ASSERT_SAME_TYPE(year_month_day, decltype(std::declval<years>() + std::declval<year_month_day>()));
+    
+    static_assert(testConstexprYears (year_month_day{year{1}, month{1}, day{1}}), "");
+
+    year_month_day ym{year{1234}, std::chrono::January, day{12}};
+    for (int i = 0; i <= 10; ++i)
+    {
+        year_month_day ym1 = ym + years{i};
+        year_month_day ym2 = years{i} + ym;
+        assert(static_cast<int>(ym1.year()) == i + 1234);
+        assert(static_cast<int>(ym2.year()) == i + 1234);
+        assert(ym1.month() == std::chrono::January);
+        assert(ym2.month() == std::chrono::January);
+        assert(ym1.day()   == day{12});
+        assert(ym2.day()   == day{12});
+        assert(ym1 == ym2);
+    }
+    }
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..063073c48
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/time.cal.ymd.nonmembers/streaming.pass.cpp
@@ -0,0 +1,58 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_day;
+
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const year_month_day& ym);
+// 
+// Returns: os << ym.year() << '/' << ym.month().
+// 
+// 
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     to_stream(basic_ostream<charT, traits>& os, const charT* fmt, const year_month_day& ym);
+// 
+// Effects: Streams ym into os using the format specified by the NTCTS fmt. fmt encoding follows the rules specified in 25.11.
+// 
+// template<class charT, class traits, class Alloc = allocator<charT>>
+//     basic_istream<charT, traits>&
+//   from_stream(basic_istream<charT, traits>& is, const charT* fmt,
+//               year_month_day& ym, basic_string<charT, traits, Alloc>* abbrev = nullptr,
+//               minutes* offset = nullptr);
+// 
+// Effects: Attempts to parse the input stream is into the year_month_day ym using the format 
+//         flags given in the NTCTS fmt as specified in 25.12. If the parse fails to decode
+//         a valid year_month_day, is.setstate(ios_- base::failbit) shall be called and ym shall
+//         not be modified. If %Z is used and successfully parsed, that value will be assigned
+//         to *abbrev if abbrev is non-null. If %z (or a modified variant) is used and 
+//         successfully parsed, that value will be assigned to *offset if offset is non-null.
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year_month_day = std::chrono::year_month_day;
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+    
+    std::cout << year_month_day{year{2018}, month{3}, day{12}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymd/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymd/types.pass.cpp
new file mode 100644
index 000000000..5ad4df53e
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymd/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year_month_day = std::chrono::year_month_day;
+    
+    static_assert(std::is_trivially_copyable_v<year_month_day>, "");
+    static_assert(std::is_standard_layout_v<year_month_day>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/ctor.pass.cpp
new file mode 100644
index 000000000..d61bdbeda
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/ctor.pass.cpp
@@ -0,0 +1,54 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day_last;
+
+//  constexpr year_month_day_last(const chrono::year& y,
+//                                const chrono::month_day_last& mdl) noexcept;
+//
+//  Effects:  Constructs an object of type year_month_day_last by initializing
+//                initializing y_ with y and mdl_ with mdl.
+//
+//  constexpr chrono::year                     year() const noexcept;
+//  constexpr chrono::month                   month() const noexcept;
+//  constexpr chrono::month_day_last month_day_last() const noexcept;
+//  constexpr bool                               ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+
+    ASSERT_NOEXCEPT(year_month_day_last{year{1}, month_day_last{month{1}}});
+    
+    constexpr month January = std::chrono::January;
+
+    constexpr year_month_day_last ymdl0{year{}, month_day_last{month{}}};
+    static_assert( ymdl0.year()           == year{},                  "");
+    static_assert( ymdl0.month()          == month{},                 "");
+    static_assert( ymdl0.month_day_last() == month_day_last{month{}}, "");
+    static_assert(!ymdl0.ok(),                                        "");
+    
+    constexpr year_month_day_last ymdl1{year{2019}, month_day_last{January}};
+    static_assert( ymdl1.year()           == year{2019},              "");
+    static_assert( ymdl1.month()          == January,                 "");
+    static_assert( ymdl1.month_day_last() == month_day_last{January}, "");
+    static_assert( ymdl1.ok(),                                        "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/day.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/day.pass.cpp
new file mode 100644
index 000000000..202b5af27
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/day.pass.cpp
@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr chrono::day day() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+
+//  TODO: wait for calendar
+//     ASSERT_NOEXCEPT(               std::declval<const year_month_day_last>().day());
+//     ASSERT_SAME_TYPE(day, decltype(std::declval<const year_month_day_last>().day()));
+// 
+//     static_assert( year_month_day_last{}.day() == day{}, "");
+
+    for (unsigned i = 1; i <= 12; ++i)
+    {
+        year_month_day_last ymd(year{1234}, month_day_last{month{i}});
+        assert( static_cast<unsigned>(ymd.day()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/month.pass.cpp
new file mode 100644
index 000000000..36fa9f4f6
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/month.pass.cpp
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr chrono::month month() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+
+    ASSERT_NOEXCEPT(                 std::declval<const year_month_day_last>().month());
+    ASSERT_SAME_TYPE(month, decltype(std::declval<const year_month_day_last>().month()));
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month_day_last ymd(year{1234}, month_day_last{month{i}});
+        assert( static_cast<unsigned>(ymd.month()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/month_day_last.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/month_day_last.pass.cpp
new file mode 100644
index 000000000..6121713e5
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/month_day_last.pass.cpp
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr chrono::day day() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+
+    ASSERT_NOEXCEPT(                          std::declval<const year_month_day_last>().month_day_last());
+    ASSERT_SAME_TYPE(month_day_last, decltype(std::declval<const year_month_day_last>().month_day_last()));
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month_day_last ymdl(year{1234}, month_day_last{month{i}});
+        assert( static_cast<unsigned>(ymdl.month_day_last().month()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/ok.pass.cpp
new file mode 100644
index 000000000..8f37cd143
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/ok.pass.cpp
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr bool ok() const noexcept;
+//  Returns: m_.ok() && y_.ok().
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+
+    constexpr month January = std::chrono::January;
+
+    ASSERT_NOEXCEPT(                std::declval<const year_month_day_last>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const year_month_day_last>().ok()));
+
+    static_assert(!year_month_day_last{year{-32768}, month_day_last{month{}}}.ok(), ""); // both bad
+    static_assert(!year_month_day_last{year{-32768}, month_day_last{January}}.ok(), ""); // Bad year
+    static_assert(!year_month_day_last{year{2019},   month_day_last{month{}}}.ok(), ""); // Bad month
+    static_assert( year_month_day_last{year{2019},   month_day_last{January}}.ok(), ""); // All OK
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        year_month_day_last ym{year{2019}, month_day_last{month{i}}};
+        assert( ym.ok() == month{i}.ok());
+    }
+
+    const int ymax = static_cast<int>(year::max());
+    for (int i = ymax - 100; i <= ymax + 100; ++i)
+    {
+        year_month_day_last ym{year{i}, month_day_last{January}};
+        assert( ym.ok() == year{i}.ok());
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/op_local_days.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/op_local_days.pass.cpp
new file mode 100644
index 000000000..845018dda
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/op_local_days.pass.cpp
@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr operator local_days() const noexcept;
+//  Returns: local_days{sys_days{*this}.time_since_epoch()}.
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+//  using sys_days            = std::chrono::local_days;
+
+//  ASSERT_NOEXCEPT(                static_cast<local_days>(std::declval<const year_month_day_last>().year()));
+//  ASSERT_SAME_TYPE(year, decltype(static_cast<local_days>(std::declval<const year_month_day_last>().year()));
+    assert(false);
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/op_sys_days.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/op_sys_days.pass.cpp
new file mode 100644
index 000000000..acb948f3a
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/op_sys_days.pass.cpp
@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr operator sys_days() const noexcept;
+//  Returns: sys_days{year()/month()/day()}.
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+//  using sys_days            = std::chrono::sys_days;
+
+//  ASSERT_NOEXCEPT(                static_cast<sys_days>(std::declval<const year_month_day_last>().year()));
+//  ASSERT_SAME_TYPE(year, decltype(static_cast<sys_days>(std::declval<const year_month_day_last>().year()));
+    assert(false);
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/plus_minus_equal_month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/plus_minus_equal_month.pass.cpp
new file mode 100644
index 000000000..0f89b24de
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/plus_minus_equal_month.pass.cpp
@@ -0,0 +1,67 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr year_month_day_last& operator+=(const months& m) noexcept;
+// constexpr year_month_day_last& operator-=(const months& m) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr(D d1)
+{
+    if (static_cast<unsigned>((d1          ).month()) !=  1) return false;
+    if (static_cast<unsigned>((d1 += Ds{ 1}).month()) !=  2) return false;
+    if (static_cast<unsigned>((d1 += Ds{ 2}).month()) !=  4) return false;
+    if (static_cast<unsigned>((d1 += Ds{12}).month()) !=  4) return false;
+    if (static_cast<unsigned>((d1 -= Ds{ 1}).month()) !=  3) return false;
+    if (static_cast<unsigned>((d1 -= Ds{ 2}).month()) !=  1) return false;
+    if (static_cast<unsigned>((d1 -= Ds{12}).month()) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+    using months              = std::chrono::months;
+
+    ASSERT_NOEXCEPT(std::declval<year_month_day_last&>() += std::declval<months>());
+    ASSERT_NOEXCEPT(std::declval<year_month_day_last&>() -= std::declval<months>());
+
+    ASSERT_SAME_TYPE(year_month_day_last&, decltype(std::declval<year_month_day_last&>() += std::declval<months>()));
+    ASSERT_SAME_TYPE(year_month_day_last&, decltype(std::declval<year_month_day_last&>() -= std::declval<months>()));
+    
+    static_assert(testConstexpr<year_month_day_last, months>(year_month_day_last{year{1234}, month_day_last{month{1}}}), "");
+
+    for (unsigned i = 0; i <= 10; ++i)
+    {
+        year y{1234};
+        month_day_last   mdl{month{i}};
+        year_month_day_last ym(y, mdl);
+        assert(static_cast<unsigned>((ym += months{2}).month()) == i + 2);
+        assert(ym.year() == y);
+        assert(static_cast<unsigned>((ym             ).month()) == i + 2);
+        assert(ym.year() == y);
+        assert(static_cast<unsigned>((ym -= months{1}).month()) == i + 1);
+        assert(ym.year() == y);
+        assert(static_cast<unsigned>((ym             ).month()) == i + 1);
+        assert(ym.year() == y);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/plus_minus_equal_year.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/plus_minus_equal_year.pass.cpp
new file mode 100644
index 000000000..e38eb9566
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/plus_minus_equal_year.pass.cpp
@@ -0,0 +1,66 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr year_month_day_last& operator+=(const years& d) noexcept;
+// constexpr year_month_day_last& operator-=(const years& d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr(D d1)
+{
+    if (static_cast<int>((d1          ).year()) !=  1) return false;
+    if (static_cast<int>((d1 += Ds{ 1}).year()) !=  2) return false;
+    if (static_cast<int>((d1 += Ds{ 2}).year()) !=  4) return false;
+    if (static_cast<int>((d1 += Ds{12}).year()) != 16) return false;
+    if (static_cast<int>((d1 -= Ds{ 1}).year()) != 15) return false;
+    if (static_cast<int>((d1 -= Ds{ 2}).year()) != 13) return false;
+    if (static_cast<int>((d1 -= Ds{12}).year()) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+    using years               = std::chrono::years;
+
+    ASSERT_NOEXCEPT(std::declval<year_month_day_last&>() += std::declval<years>());
+    ASSERT_NOEXCEPT(std::declval<year_month_day_last&>() -= std::declval<years>());
+
+    ASSERT_SAME_TYPE(year_month_day_last&, decltype(std::declval<year_month_day_last&>() += std::declval<years>()));
+    ASSERT_SAME_TYPE(year_month_day_last&, decltype(std::declval<year_month_day_last&>() -= std::declval<years>()));
+    
+    static_assert(testConstexpr<year_month_day_last, years>(year_month_day_last{year{1}, month_day_last{month{1}}}), "");
+
+    for (int i = 1000; i <= 1010; ++i)
+    {
+        month_day_last mdl{month{2}};
+        year_month_day_last ymdl(year{i}, mdl);
+        assert(static_cast<int>((ymdl += years{2}).year()) == i + 2);
+        assert(ymdl.month_day_last() == mdl);
+        assert(static_cast<int>((ymdl            ).year()) == i + 2);
+        assert(ymdl.month_day_last() == mdl);
+        assert(static_cast<int>((ymdl -= years{1}).year()) == i + 1);
+        assert(ymdl.month_day_last() == mdl);
+        assert(static_cast<int>((ymdl            ).year()) == i + 1);
+        assert(ymdl.month_day_last() == mdl);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/year.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/year.pass.cpp
new file mode 100644
index 000000000..0e79d781b
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.members/year.pass.cpp
@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr chrono::day day() const noexcept;
+//  Returns: d_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+
+    ASSERT_NOEXCEPT(                std::declval<const year_month_day_last>().year());
+    ASSERT_SAME_TYPE(year, decltype(std::declval<const year_month_day_last>().year()));
+
+    for (int i = 1; i <= 50; ++i)
+    {
+        year_month_day_last ym(year{i}, month_day_last{month{}});
+        assert( static_cast<int>(ym.year()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..303f28646
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,88 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr bool operator==(const year_month_day_last& x, const year_month_day_last& y) noexcept;
+//   Returns: x.year() == y.year() && x.month_day_last() == y.month_day_last().
+//
+// constexpr bool operator< (const year_month_day_last& x, const year_month_day_last& y) noexcept;
+//   Returns: 
+//      If x.year() < y.year(), returns true. 
+//      Otherwise, if x.year() > y.year(), returns false.
+//      Otherwise, returns x.month_day_last() < y.month_day_last()
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+
+    AssertComparisons6AreNoexcept<year_month_day_last>();
+    AssertComparisons6ReturnBool<year_month_day_last>();
+    
+    constexpr month January = std::chrono::January;
+    constexpr month February = std::chrono::February;
+
+    static_assert( testComparisons6(
+        year_month_day_last{year{1234}, month_day_last{January}}, 
+        year_month_day_last{year{1234}, month_day_last{January}},
+        true, false), "");
+    
+//  different month
+    static_assert( testComparisons6(
+        year_month_day_last{year{1234}, month_day_last{January}},
+        year_month_day_last{year{1234}, month_day_last{February}},
+        false, true), "");
+
+//  different year
+    static_assert( testComparisons6(
+        year_month_day_last{year{1234}, month_day_last{January}},
+        year_month_day_last{year{1235}, month_day_last{January}},
+        false, true), "");
+
+//  different month
+    static_assert( testComparisons6(
+        year_month_day_last{year{1234}, month_day_last{January}},
+        year_month_day_last{year{1234}, month_day_last{February}},
+        false, true), "");
+
+//  different year and month
+    static_assert( testComparisons6(
+        year_month_day_last{year{1234}, month_day_last{February}},
+        year_month_day_last{year{1235}, month_day_last{January}},
+        false, true), "");
+
+//  same year, different months
+    for (unsigned i = 1; i < 12; ++i)
+        for (unsigned j = 1; j < 12; ++j)
+            assert((testComparisons6(
+                year_month_day_last{year{1234}, month_day_last{month{i}}}, 
+                year_month_day_last{year{1234}, month_day_last{month{j}}}, 
+                i == j, i < j )));
+    
+//  same month, different years
+    for (int i = 1000; i < 20; ++i)
+        for (int j = 1000; j < 20; ++j)
+        assert((testComparisons6(
+            year_month_day_last{year{i}, month_day_last{January}}, 
+            year_month_day_last{year{j}, month_day_last{January}},
+            i == j, i < j )));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/minus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/minus.pass.cpp
new file mode 100644
index 000000000..950b1005b
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/minus.pass.cpp
@@ -0,0 +1,92 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr year_month_day_last
+//   operator-(const year_month_day_last& ymdl, const months& dm) noexcept;
+// 
+//   Returns: ymdl + (-dm).
+//
+// constexpr year_month_day_last
+//   operator-(const year_month_day_last& ymdl, const years& dy) noexcept;
+// 
+//   Returns: ymdl + (-dy).
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+#include <iostream>
+
+constexpr bool testConstexprYears (std::chrono::year_month_day_last ymdl)
+{
+    std::chrono::year_month_day_last ym1 = ymdl - std::chrono::years{10};
+    return
+        ym1.year()  == std::chrono::year{static_cast<int>(ymdl.year()) - 10}
+     && ym1.month() == ymdl.month()
+        ;
+}
+
+constexpr bool testConstexprMonths (std::chrono::year_month_day_last ymdl)
+{
+    std::chrono::year_month_day_last ym1 = ymdl - std::chrono::months{6};
+    return
+        ym1.year()  == ymdl.year()
+     && ym1.month() == std::chrono::month{static_cast<unsigned>(ymdl.month()) - 6}
+        ;
+}
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+    using months              = std::chrono::months;
+    using years               = std::chrono::years;
+
+    constexpr month December = std::chrono::December;
+
+    { // year_month_day_last - years
+    ASSERT_NOEXCEPT(                               std::declval<year_month_day_last>() - std::declval<years>());
+    ASSERT_SAME_TYPE(year_month_day_last, decltype(std::declval<year_month_day_last>() - std::declval<years>()));
+
+    static_assert(testConstexprYears(year_month_day_last{year{1234}, month_day_last{December}}), "");
+    year_month_day_last ym{year{1234}, month_day_last{December}};
+    for (int i = 0; i <= 10; ++i)
+    {
+        year_month_day_last ym1 = ym - years{i};
+        assert(static_cast<int>(ym1.year()) == 1234 - i);
+        assert(ym1.month() == December);
+    }
+    }
+
+    { // year_month_day_last - months
+    ASSERT_NOEXCEPT(                               std::declval<year_month_day_last>() - std::declval<months>());
+    ASSERT_SAME_TYPE(year_month_day_last, decltype(std::declval<year_month_day_last>() - std::declval<months>()));
+
+    static_assert(testConstexprMonths(year_month_day_last{year{1234}, month_day_last{December}}), "");
+//  TODO test wrapping
+    year_month_day_last ym{year{1234}, month_day_last{December}};
+    for (unsigned i = 0; i <= 10; ++i)
+    {
+        year_month_day_last ym1 = ym - months{i};
+        assert(static_cast<int>(ym1.year()) == 1234);
+        assert(static_cast<unsigned>(ym1.month()) == 12U-i);
+    }
+    }
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/plus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/plus.pass.cpp
new file mode 100644
index 000000000..5cf3151ec
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/plus.pass.cpp
@@ -0,0 +1,123 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr year_month_day_last
+//   operator+(const year_month_day_last& ymdl, const months& dm) noexcept;
+//
+//   Returns: (ymdl.year() / ymdl.month() + dm) / last.
+// 
+// constexpr year_month_day_last
+//   operator+(const months& dm, const year_month_day_last& ymdl) noexcept;
+//
+//   Returns: ymdl + dm.
+//
+//
+// constexpr year_month_day_last 
+//   operator+(const year_month_day_last& ymdl, const years& dy) noexcept;
+//
+//   Returns: {ymdl.year()+dy, ymdl.month_day_last()}.
+// 
+// constexpr year_month_day_last
+//   operator+(const years& dy, const year_month_day_last& ymdl) noexcept;
+//
+//   Returns: ymdl + dy 
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool testConstexprYears(std::chrono::year_month_day_last ymdl)
+{
+    std::chrono::years offset{23};
+    if (static_cast<int>((ymdl         ).year()) !=  1)           return false;
+    if (static_cast<int>((ymdl + offset).year()) != 24)           return false;
+    if (                 (ymdl + offset).month() != ymdl.month()) return false;
+    if (static_cast<int>((offset + ymdl).year()) != 24)           return false;
+    if (                 (offset + ymdl).month() != ymdl.month()) return false;
+    return true;
+}
+
+
+constexpr bool testConstexprMonths(std::chrono::year_month_day_last ymdl)
+{
+    std::chrono::months offset{6};
+    if (static_cast<unsigned>((ymdl         ).month()) !=  1)          return false;
+    if (                      (ymdl + offset).year()   != ymdl.year()) return false;
+    if (static_cast<unsigned>((ymdl + offset).month()) !=  7)          return false;
+    if (static_cast<unsigned>((offset + ymdl).month()) !=  7)          return false;
+    if (                      (offset + ymdl).year()   != ymdl.year()) return false;
+    return true;
+}
+
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+    using months              = std::chrono::months;
+    using years               = std::chrono::years;
+
+    constexpr month January = std::chrono::January;
+
+    {   // year_month_day_last + months
+    ASSERT_NOEXCEPT(std::declval<year_month_day_last>() + std::declval<months>());
+    ASSERT_NOEXCEPT(std::declval<months>() + std::declval<year_month_day_last>());
+
+    ASSERT_SAME_TYPE(year_month_day_last, decltype(std::declval<year_month_day_last>() + std::declval<months>()));
+    ASSERT_SAME_TYPE(year_month_day_last, decltype(std::declval<months>() + std::declval<year_month_day_last>()));
+
+    static_assert(testConstexprMonths(year_month_day_last{year{1}, month_day_last{January}}), "");
+
+    year_month_day_last ym{year{1234}, month_day_last{January}};
+    for (int i = 0; i <= 10; ++i)  // TODO test wrap-around
+    {
+        year_month_day_last ym1 = ym + months{i};
+        year_month_day_last ym2 = months{i} + ym;
+        assert(static_cast<int>(ym1.year()) == 1234);
+        assert(static_cast<int>(ym2.year()) == 1234);
+        assert(ym1.month() == month(1 + i));
+        assert(ym2.month() == month(1 + i));
+        assert(ym1 == ym2);
+    }
+    }
+
+    {   // year_month_day_last + years
+    ASSERT_NOEXCEPT(std::declval<year_month_day_last>() + std::declval<years>());
+    ASSERT_NOEXCEPT(std::declval<years>() + std::declval<year_month_day_last>());
+
+    ASSERT_SAME_TYPE(year_month_day_last, decltype(std::declval<year_month_day_last>() + std::declval<years>()));
+    ASSERT_SAME_TYPE(year_month_day_last, decltype(std::declval<years>() + std::declval<year_month_day_last>()));
+    
+    static_assert(testConstexprYears(year_month_day_last{year{1}, month_day_last{January}}), "");
+
+    year_month_day_last ym{year{1234}, month_day_last{January}};
+    for (int i = 0; i <= 10; ++i)
+    {
+        year_month_day_last ym1 = ym + years{i};
+        year_month_day_last ym2 = years{i} + ym;
+        assert(static_cast<int>(ym1.year()) == i + 1234);
+        assert(static_cast<int>(ym2.year()) == i + 1234);
+        assert(ym1.month() == std::chrono::January);
+        assert(ym2.month() == std::chrono::January);
+        assert(ym1 == ym2);
+    }
+    }
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..3d218d125
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymdlast/time.cal.ymdlast.nonmembers/streaming.pass.cpp
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_day_last;
+
+// template<class charT, class traits>
+//   basic_ostream<charT, traits>&
+//   operator<<(basic_ostream<charT, traits>& os, const year_month_day_last& ymdl);
+// 
+// Returns: os << ymdl.year() << '/' << ymdl.month_day_last().
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year_month_day_last = std::chrono::year_month_day_last;
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using month_day_last      = std::chrono::month_day_last;
+
+    std::cout << year_month_day_last{year{2018}, month_day_last{month{3}}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.local_days.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.local_days.pass.cpp
new file mode 100644
index 000000000..a13e7c772
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.local_days.pass.cpp
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_weekday;
+
+//  explicit constexpr year_month_weekday(const local_days& dp) noexcept;
+//
+//
+//  Effects:  Constructs an object of type year_month_weekday that corresponds 
+//                to the date represented by dp
+//
+//  Remarks: Equivalent to constructing with sys_days{dp.time_since_epoch()}.
+//
+//  constexpr chrono::year   year() const noexcept;
+//  constexpr chrono::month month() const noexcept;
+//  constexpr chrono::day     day() const noexcept;
+//  constexpr bool             ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+//  using local_days     = std::chrono::local_days;
+    using year_month_weekday = std::chrono::year_month_weekday;
+
+//  ASSERT_NOEXCEPT(year_month_weekday{std::declval<const local_days>()});
+    assert(false);
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.pass.cpp
new file mode 100644
index 000000000..a7ee7b275
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.pass.cpp
@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+//  year_month_weekday() = default;
+//  constexpr year_month_weekday(const chrono::year& y, const chrono::month& m,
+//                               const chrono::weekday_indexed& wdi) noexcept;
+//
+//  Effects:  Constructs an object of type year_month_weekday by initializing
+//                y_ with y, m_ with m, and wdi_ with wdi.
+//
+//  constexpr chrono::year                       year() const noexcept;
+//  constexpr chrono::month                     month() const noexcept;
+//  constexpr chrono::weekday                 weekday() const noexcept;
+//  constexpr unsigned                          index() const noexcept;
+//  constexpr chrono::weekday_indexed weekday_indexed() const noexcept;
+//  constexpr bool                                 ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+
+    constexpr month January = std::chrono::January;
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+
+    ASSERT_NOEXCEPT(year_month_weekday{});
+    ASSERT_NOEXCEPT(year_month_weekday{year{1}, month{1}, weekday_indexed{Tuesday, 1}});
+    
+    constexpr year_month_weekday ym0{};
+    static_assert( ym0.year()            == year{},            "");
+    static_assert( ym0.month()           == month{},           "");
+    static_assert( ym0.weekday()         == weekday{},         "");
+    static_assert( ym0.index()           == 0,                 "");
+    static_assert( ym0.weekday_indexed() == weekday_indexed{}, "");
+    static_assert(!ym0.ok(),                                   "");
+
+    constexpr year_month_weekday ym1{year{2019}, January, weekday_indexed{Tuesday, 1}};
+    static_assert( ym1.year()            == year{2019},                  "");
+    static_assert( ym1.month()           == January,                     "");
+    static_assert( ym1.weekday()         == Tuesday,                     "");
+    static_assert( ym1.index()           == 1,                           "");
+    static_assert( ym1.weekday_indexed() == weekday_indexed{Tuesday, 1}, "");
+    static_assert( ym1.ok(),                                             "");
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.sys_days.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.sys_days.pass.cpp
new file mode 100644
index 000000000..e3ae2235e
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.sys_days.pass.cpp
@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_weekday;
+
+//  constexpr year_month_weekday(const sys_days& dp) noexcept;
+//
+//  Effects:  Constructs an object of type year_month_weekday that corresponds 
+//                to the date represented by dp
+//
+//  Remarks: For any value ymd of type year_month_weekday for which ymd.ok() is true, 
+//                ymd == year_month_weekday{sys_days{ymd}} is true.
+//
+//  constexpr chrono::year   year() const noexcept;
+//  constexpr chrono::month month() const noexcept;
+//  constexpr bool             ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year           = std::chrono::year;
+    using month          = std::chrono::month;
+    using day            = std::chrono::day;
+//  using sys_days     = std::chrono::sys_days;
+    using year_month_weekday = std::chrono::year_month_weekday;
+
+//  ASSERT_NOEXCEPT(year_month_weekday{std::declval<const sys_days>()});
+    assert(false);
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.year_month_day_last.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.year_month_day_last.pass.cpp
new file mode 100644
index 000000000..20e48cb77
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ctor.year_month_day_last.pass.cpp
@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_weekday;
+
+//  constexpr year_month_weekday(const year_month_weekday_last& ymdl) noexcept;
+//
+//  Effects:  Constructs an object of type year_month_weekday by initializing
+//              y_ with ymdl.year(), m_ with ymdl.month(), and d_ with ymdl.day().
+//
+//  constexpr chrono::year   year() const noexcept;
+//  constexpr chrono::month month() const noexcept;
+//  constexpr chrono::day     day() const noexcept;
+//  constexpr bool             ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+    using year_month_weekday      = std::chrono::year_month_weekday;
+
+    ASSERT_NOEXCEPT(year_month_weekday{std::declval<const year_month_weekday_last>()});
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/index.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/index.pass.cpp
new file mode 100644
index 000000000..6fbac7f68
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/index.pass.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr unsigned index() const noexcept;
+//  Returns: wdi_.index()
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+
+    ASSERT_NOEXCEPT(                    std::declval<const year_month_weekday>().index());
+    ASSERT_SAME_TYPE(unsigned, decltype(std::declval<const year_month_weekday>().index()));
+
+    static_assert( year_month_weekday{}.index() == 0, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month_weekday ymwd0(year{1234}, month{2}, weekday_indexed{weekday{2}, i});
+        assert(ymwd0.index() == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/month.pass.cpp
new file mode 100644
index 000000000..67f9217e0
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/month.pass.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr chrono::month month() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+
+    ASSERT_NOEXCEPT(                 std::declval<const year_month_weekday>().month());
+    ASSERT_SAME_TYPE(month, decltype(std::declval<const year_month_weekday>().month()));
+
+    static_assert( year_month_weekday{}.month() == month{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month_weekday ymd(year{1234}, month{i}, weekday_indexed{});
+        assert( static_cast<unsigned>(ymd.month()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ok.pass.cpp
new file mode 100644
index 000000000..e2776f885
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/ok.pass.cpp
@@ -0,0 +1,76 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr bool ok() const noexcept;
+//  Returns: m_.ok() && y_.ok().
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+
+    constexpr month January = std::chrono::January;
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+
+    ASSERT_NOEXCEPT(                std::declval<const year_month_weekday>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const year_month_weekday>().ok()));
+
+    static_assert(!year_month_weekday{}.ok(), "");
+
+    static_assert(!year_month_weekday{year{-32768}, month{}, weekday_indexed{}}.ok(),           ""); // All three bad
+
+    static_assert(!year_month_weekday{year{-32768}, January, weekday_indexed{Tuesday, 1}}.ok(), ""); // Bad year
+    static_assert(!year_month_weekday{year{2019},   month{}, weekday_indexed{Tuesday, 1}}.ok(), ""); // Bad month
+    static_assert(!year_month_weekday{year{2019},   January, weekday_indexed{} }.ok(),          ""); // Bad day
+
+    static_assert(!year_month_weekday{year{-32768}, month{}, weekday_indexed{Tuesday, 1}}.ok(), ""); // Bad year & month
+    static_assert(!year_month_weekday{year{2019},   month{}, weekday_indexed{} }.ok(),          ""); // Bad month & day
+    static_assert(!year_month_weekday{year{-32768}, January, weekday_indexed{} }.ok(),          ""); // Bad year & day
+
+    static_assert( year_month_weekday{year{2019},   January, weekday_indexed{Tuesday, 1}}.ok(), ""); // All OK
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        year_month_weekday ym{year{2019}, January, weekday_indexed{Tuesday, i}};
+        assert((ym.ok() == weekday_indexed{Tuesday, i}.ok()));
+    }
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        year_month_weekday ym{year{2019}, January, weekday_indexed{weekday{i}, 1}};
+        assert((ym.ok() == weekday_indexed{weekday{i}, 1}.ok()));
+    }
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        year_month_weekday ym{year{2019}, month{i}, weekday_indexed{Tuesday, 1}};
+        assert((ym.ok() == month{i}.ok()));
+    }
+
+    const int ymax = static_cast<int>(year::max());
+    for (int i = ymax - 100; i <= ymax + 100; ++i)
+    {
+        year_month_weekday ym{year{i}, January, weekday_indexed{Tuesday, 1}};
+        assert((ym.ok() == year{i}.ok()));
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/plus_minus_equal_month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/plus_minus_equal_month.pass.cpp
new file mode 100644
index 000000000..55aa86d89
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/plus_minus_equal_month.pass.cpp
@@ -0,0 +1,82 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr year_month_weekday& operator+=(const months& m) noexcept;
+// constexpr year_month_weekday& operator-=(const months& m) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr(D d1)
+{
+    if (static_cast<unsigned>((d1          ).month()) !=  1) return false;
+    if (static_cast<unsigned>((d1 += Ds{ 1}).month()) !=  2) return false;
+    if (static_cast<unsigned>((d1 += Ds{ 2}).month()) !=  4) return false;
+    if (static_cast<unsigned>((d1 += Ds{12}).month()) !=  4) return false;
+    if (static_cast<unsigned>((d1 -= Ds{ 1}).month()) !=  3) return false;
+    if (static_cast<unsigned>((d1 -= Ds{ 2}).month()) !=  1) return false;
+    if (static_cast<unsigned>((d1 -= Ds{12}).month()) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+    using years              = std::chrono::years;
+    using months             = std::chrono::months;
+
+
+    ASSERT_NOEXCEPT(                               std::declval<year_month_weekday&>() += std::declval<months>());
+    ASSERT_SAME_TYPE(year_month_weekday&, decltype(std::declval<year_month_weekday&>() += std::declval<months>()));
+
+    ASSERT_NOEXCEPT(                               std::declval<year_month_weekday&>() -= std::declval<months>());
+    ASSERT_SAME_TYPE(year_month_weekday&, decltype(std::declval<year_month_weekday&>() -= std::declval<months>()));
+
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    static_assert(testConstexpr<year_month_weekday, months>(year_month_weekday{year{1234}, month{1}, weekday_indexed{Tuesday, 2}}), "");
+
+    for (unsigned i = 0; i <= 10; ++i)
+    {
+        year y{1234};
+        year_month_weekday ymwd(y, month{i}, weekday_indexed{Tuesday, 2});
+
+        assert(static_cast<unsigned>((ymwd += months{2}).month()) == i + 2);
+        assert(ymwd.year()     == y);
+        assert(ymwd.weekday()  == Tuesday);
+        assert(ymwd.index()    == 2);
+
+        assert(static_cast<unsigned>((ymwd             ).month()) == i + 2);
+        assert(ymwd.year()     == y);
+        assert(ymwd.weekday()  == Tuesday);
+        assert(ymwd.index()    == 2);
+
+        assert(static_cast<unsigned>((ymwd -= months{1}).month()) == i + 1);
+        assert(ymwd.year()     == y);
+        assert(ymwd.weekday()  == Tuesday);
+        assert(ymwd.index()    == 2);
+
+        assert(static_cast<unsigned>((ymwd             ).month()) == i + 1);
+        assert(ymwd.year()     == y);
+        assert(ymwd.weekday()  == Tuesday);
+        assert(ymwd.index()    == 2);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/plus_minus_equal_year.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/plus_minus_equal_year.pass.cpp
new file mode 100644
index 000000000..10ba6c64b
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/plus_minus_equal_year.pass.cpp
@@ -0,0 +1,82 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr year_month_weekday& operator+=(const years& d) noexcept;
+// constexpr year_month_weekday& operator-=(const years& d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr(D d1)
+{
+    if (static_cast<int>((d1          ).year()) !=  1) return false;
+    if (static_cast<int>((d1 += Ds{ 1}).year()) !=  2) return false;
+    if (static_cast<int>((d1 += Ds{ 2}).year()) !=  4) return false;
+    if (static_cast<int>((d1 += Ds{12}).year()) != 16) return false;
+    if (static_cast<int>((d1 -= Ds{ 1}).year()) != 15) return false;
+    if (static_cast<int>((d1 -= Ds{ 2}).year()) != 13) return false;
+    if (static_cast<int>((d1 -= Ds{12}).year()) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+    using years              = std::chrono::years;
+    using months             = std::chrono::months;
+
+    ASSERT_NOEXCEPT(                               std::declval<year_month_weekday&>() += std::declval<years>());
+    ASSERT_SAME_TYPE(year_month_weekday&, decltype(std::declval<year_month_weekday&>() += std::declval<years>()));
+
+    ASSERT_NOEXCEPT(                               std::declval<year_month_weekday&>() -= std::declval<years>());
+    ASSERT_SAME_TYPE(year_month_weekday&, decltype(std::declval<year_month_weekday&>() -= std::declval<years>()));
+    
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    constexpr month January = std::chrono::January;
+
+    static_assert(testConstexpr<year_month_weekday, years>(year_month_weekday{year{1}, January, weekday_indexed{Tuesday, 2}}), "");
+
+    for (int i = 1000; i <= 1010; ++i)
+    {
+        year_month_weekday ymwd(year{i}, January, weekday_indexed{Tuesday, 2});
+
+        assert(static_cast<int>((ymwd += years{2}).year()) == i + 2);
+        assert(ymwd.month()    == January);
+        assert(ymwd.weekday()  == Tuesday);
+        assert(ymwd.index()    == 2);
+
+        assert(static_cast<int>((ymwd            ).year()) == i + 2);
+        assert(ymwd.month()    == January);
+        assert(ymwd.weekday()  == Tuesday);
+        assert(ymwd.index()    == 2);
+
+        assert(static_cast<int>((ymwd -= years{1}).year()) == i + 1);
+        assert(ymwd.month()    == January);
+        assert(ymwd.weekday()  == Tuesday);
+        assert(ymwd.index()    == 2);
+
+        assert(static_cast<int>((ymwd            ).year()) == i + 1);
+        assert(ymwd.month()    == January);
+        assert(ymwd.weekday()  == Tuesday);
+        assert(ymwd.index()    == 2);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/weekday.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/weekday.pass.cpp
new file mode 100644
index 000000000..6241a0768
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/weekday.pass.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr chrono::weekday weekday() const noexcept;
+//  Returns: wdi_.weekday()
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+
+    ASSERT_NOEXCEPT(                   std::declval<const year_month_weekday>().weekday());
+    ASSERT_SAME_TYPE(weekday, decltype(std::declval<const year_month_weekday>().weekday()));
+
+    static_assert( year_month_weekday{}.weekday() == weekday{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month_weekday ymwd0(year{1234}, month{2}, weekday_indexed{weekday{i}, 1});
+        assert(static_cast<unsigned>(ymwd0.weekday()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/weekday_indexed.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/weekday_indexed.pass.cpp
new file mode 100644
index 000000000..da096135e
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/weekday_indexed.pass.cpp
@@ -0,0 +1,46 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr chrono::weekday_indexed weekday_indexed() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+
+    ASSERT_NOEXCEPT(                           std::declval<const year_month_weekday>().weekday_indexed());
+    ASSERT_SAME_TYPE(weekday_indexed, decltype(std::declval<const year_month_weekday>().weekday_indexed()));
+
+    static_assert( year_month_weekday{}.weekday_indexed() == weekday_indexed{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month_weekday ymwd0(year{1234}, month{2}, weekday_indexed{weekday{i}, 1});
+        assert( static_cast<unsigned>(ymwd0.weekday_indexed().weekday()) == i);
+        assert( static_cast<unsigned>(ymwd0.weekday_indexed().index()) == 1);
+        year_month_weekday ymwd1(year{1234}, month{2}, weekday_indexed{weekday{2}, i});
+        assert( static_cast<unsigned>(ymwd1.weekday_indexed().weekday()) == 2);
+        assert( static_cast<unsigned>(ymwd1.weekday_indexed().index()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/year.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/year.pass.cpp
new file mode 100644
index 000000000..7db843959
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.members/year.pass.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr chrono::year year() const noexcept;
+//  Returns: d_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+
+    ASSERT_NOEXCEPT(                std::declval<const year_month_weekday>().year());
+    ASSERT_SAME_TYPE(year, decltype(std::declval<const year_month_weekday>().year()));
+
+    static_assert( year_month_weekday{}.year() == year{}, "");
+
+    for (int i = 1; i <= 50; ++i)
+    {
+        year_month_weekday ym(year{i}, month{1}, weekday_indexed{});
+        assert( static_cast<int>(ym.year()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..6e8f7c03d
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,114 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr bool operator==(const year_month_weekday& x, const year_month_weekday& y) noexcept;
+//   Returns: x.year() == y.year() && x.month() == y.month() && x.weekday_indexed() == y.weekday_indexed()
+//
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using weekday            = std::chrono::weekday;
+    using year_month_weekday = std::chrono::year_month_weekday;
+
+    AssertComparisons2AreNoexcept<year_month_weekday>();
+    AssertComparisons2ReturnBool<year_month_weekday>();
+    
+    constexpr month January   = std::chrono::January;
+    constexpr month February  = std::chrono::February;
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+
+    static_assert( testComparisons2(
+        year_month_weekday{year{1234}, January, weekday_indexed{Tuesday, 1}}, 
+        year_month_weekday{year{1234}, January, weekday_indexed{Tuesday, 1}},
+        true), "");
+    
+//  different day
+    static_assert( testComparisons2(
+        year_month_weekday{year{1234}, January, weekday_indexed{Tuesday, 1}}, 
+        year_month_weekday{year{1234}, January, weekday_indexed{Tuesday, 2}},
+        false), "");
+    
+//  different month
+    static_assert( testComparisons2(
+        year_month_weekday{year{1234}, January,  weekday_indexed{Tuesday, 1}},
+        year_month_weekday{year{1234}, February, weekday_indexed{Tuesday, 1}},
+        false), "");
+
+//  different year
+    static_assert( testComparisons2(
+        year_month_weekday{year{1234}, January, weekday_indexed{Tuesday, 1}},
+        year_month_weekday{year{1235}, January, weekday_indexed{Tuesday, 1}},
+        false), "");
+
+
+//  different month and day
+    static_assert( testComparisons2(
+        year_month_weekday{year{1234}, January,  weekday_indexed{Tuesday, 1}},
+        year_month_weekday{year{1234}, February, weekday_indexed{Tuesday, 2}},
+        false), "");
+
+//  different year and month
+    static_assert( testComparisons2(
+        year_month_weekday{year{1234}, February, weekday_indexed{Tuesday, 1}},
+        year_month_weekday{year{1235}, January,  weekday_indexed{Tuesday, 1}},
+        false), "");
+
+//  different year and day
+    static_assert( testComparisons2(
+        year_month_weekday{year{1234}, January, weekday_indexed{Tuesday, 2}},
+        year_month_weekday{year{1235}, January, weekday_indexed{Tuesday, 1}},
+        false), "");
+
+//  different year, month and day
+    static_assert( testComparisons2(
+        year_month_weekday{year{1234}, February, weekday_indexed{Tuesday, 2}},
+        year_month_weekday{year{1235}, January,  weekday_indexed{Tuesday, 1}},
+        false), "");
+
+
+//  same year, different days
+    for (unsigned i = 1; i < 28; ++i)
+        for (unsigned j = 1; j < 28; ++j)
+            assert((testComparisons2(
+                year_month_weekday{year{1234}, January, weekday_indexed{Tuesday, i}},
+                year_month_weekday{year{1234}, January, weekday_indexed{Tuesday, j}},
+                i == j)));
+    
+//  same year, different months
+    for (unsigned i = 1; i < 12; ++i)
+        for (unsigned j = 1; j < 12; ++j)
+            assert((testComparisons2(
+                year_month_weekday{year{1234}, month{i}, weekday_indexed{Tuesday, 1}},
+                year_month_weekday{year{1234}, month{j}, weekday_indexed{Tuesday, 1}},
+                i == j)));
+    
+//  same month, different years
+    for (int i = 1000; i < 20; ++i)
+        for (int j = 1000; j < 20; ++j)
+        assert((testComparisons2(
+            year_month_weekday{year{i}, January, weekday_indexed{Tuesday, 1}},
+            year_month_weekday{year{j}, January, weekday_indexed{Tuesday, 1}},
+            i == j)));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/minus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/minus.pass.cpp
new file mode 100644
index 000000000..a92811cc3
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/minus.pass.cpp
@@ -0,0 +1,101 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr year_month_weekday operator-(const year_month_weekday& ymwd, const months& dm) noexcept;
+//   Returns: ymwd + (-dm).
+// 
+// constexpr year_month_weekday operator-(const year_month_weekday& ymwd, const years& dy) noexcept;
+//   Returns: ymwd + (-dy).
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+#include <iostream>
+
+constexpr bool testConstexprYears ()
+{
+    std::chrono::year_month_weekday ym0{std::chrono::year{1234}, std::chrono::January, std::chrono::weekday_indexed{std::chrono::Tuesday, 1}};
+    std::chrono::year_month_weekday ym1 = ym0 - std::chrono::years{10};
+    return
+        ym1.year()    == std::chrono::year{1234-10}
+     && ym1.month()   == std::chrono::January
+     && ym1.weekday() == std::chrono::Tuesday
+     && ym1.index()   == 1
+        ;
+}
+
+constexpr bool testConstexprMonths ()
+{
+    std::chrono::year_month_weekday ym0{std::chrono::year{1234}, std::chrono::November, std::chrono::weekday_indexed{std::chrono::Tuesday, 1}};
+    std::chrono::year_month_weekday ym1 = ym0 - std::chrono::months{6};
+    return
+        ym1.year()    == std::chrono::year{1234}
+     && ym1.month()   == std::chrono::May
+     && ym1.weekday() == std::chrono::Tuesday
+     && ym1.index()   == 1
+        ;
+}
+
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+    using years              = std::chrono::years;
+    using months             = std::chrono::months;
+
+    constexpr month November  = std::chrono::November;
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+
+    {  // year_month_weekday - years
+    ASSERT_NOEXCEPT(                              std::declval<year_month_weekday>() - std::declval<years>());
+    ASSERT_SAME_TYPE(year_month_weekday, decltype(std::declval<year_month_weekday>() - std::declval<years>()));
+
+    static_assert(testConstexprYears(), "");
+    
+    year_month_weekday ym{year{1234}, November, weekday_indexed{Tuesday, 1}};
+    for (int i = 0; i <= 10; ++i)
+    {
+        year_month_weekday ym1 = ym - years{i};
+        assert(static_cast<int>(ym1.year()) == 1234 - i);
+        assert(ym1.month()   == November);
+        assert(ym1.weekday() == Tuesday);
+        assert(ym1.index()   == 1);
+    }
+    }
+    
+    {  // year_month_weekday - months
+    ASSERT_NOEXCEPT(                              std::declval<year_month_weekday>() - std::declval<months>());
+    ASSERT_SAME_TYPE(year_month_weekday, decltype(std::declval<year_month_weekday>() - std::declval<months>()));
+
+    static_assert(testConstexprMonths(), "");
+    
+    year_month_weekday ym{year{1234}, November, weekday_indexed{Tuesday, 2}};
+    for (unsigned i = 1; i <= 10; ++i)
+    {
+        year_month_weekday ym1 = ym - months{i};
+        assert(ym1.year()    == year{1234});
+        assert(ym1.month()   == month{11-i});
+        assert(ym1.weekday() == Tuesday);
+        assert(ym1.index()   == 2);
+    }
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/plus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/plus.pass.cpp
new file mode 100644
index 000000000..38838fb69
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/plus.pass.cpp
@@ -0,0 +1,121 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+// constexpr year_month_weekday operator+(const year_month_weekday& ymd, const months& dm) noexcept;
+//   Returns: (ymd.year() / ymd.month() + dm) / ymd.day().
+// 
+// constexpr year_month_weekday operator+(const months& dm, const year_month_weekday& ymd) noexcept;
+//   Returns: ymd + dm.
+//
+//
+// constexpr year_month_weekday operator+(const year_month_weekday& ymd, const years& dy) noexcept;
+//   Returns: (ymd.year() + dy) / ymd.month() / ymd.day().
+// 
+// constexpr year_month_weekday operator+(const years& dy, const year_month_weekday& ymd) noexcept;
+//   Returns: ym + dm.
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool testConstexprYears(std::chrono::year_month_weekday ym)
+{
+    std::chrono::years offset{23};
+    if (static_cast<int>((ym         ).year()) !=  1) return false;
+    if (static_cast<int>((ym + offset).year()) != 24) return false;
+    if (static_cast<int>((offset + ym).year()) != 24) return false;
+    return true;
+}
+
+
+constexpr bool testConstexprMonths(std::chrono::year_month_weekday ym)
+{
+    std::chrono::months offset{6};
+    if (static_cast<unsigned>((ym         ).month()) !=  1) return false;
+    if (static_cast<unsigned>((ym + offset).month()) !=  7) return false;
+    if (static_cast<unsigned>((offset + ym).month()) !=  7) return false;
+    return true;
+}
+
+
+int main()
+{
+    using year               = std::chrono::year;
+    using month              = std::chrono::month;
+    using day                = std::chrono::day;
+    using weekday            = std::chrono::weekday;
+    using weekday_indexed    = std::chrono::weekday_indexed;
+    using year_month_weekday = std::chrono::year_month_weekday;
+    using years              = std::chrono::years;
+    using months             = std::chrono::months;
+
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    constexpr month January = std::chrono::January;
+
+    {   // year_month_weekday + months (and switched)
+    ASSERT_NOEXCEPT(std::declval<year_month_weekday>() + std::declval<months>());
+    ASSERT_NOEXCEPT(std::declval<months>() + std::declval<year_month_weekday>());
+
+    ASSERT_SAME_TYPE(year_month_weekday, decltype(std::declval<year_month_weekday>() + std::declval<months>()));
+    ASSERT_SAME_TYPE(year_month_weekday, decltype(std::declval<months>() + std::declval<year_month_weekday>()));
+
+    static_assert(testConstexprMonths(year_month_weekday{year{1}, January, weekday_indexed{Tuesday, 1}}), "");
+
+    year_month_weekday ym{year{1234}, January, weekday_indexed{Tuesday, 3}};
+    for (int i = 0; i <= 10; ++i)  // TODO test wrap-around
+    {
+        year_month_weekday ym1 = ym + months{i};
+        year_month_weekday ym2 = months{i} + ym;
+        assert(static_cast<int>(ym1.year()) == 1234);
+        assert(static_cast<int>(ym2.year()) == 1234);
+        assert(ym1.month()   == month(1 + i));
+        assert(ym2.month()   == month(1 + i));
+        assert(ym1.weekday() == Tuesday);
+        assert(ym2.weekday() == Tuesday);
+        assert(ym1.index()   == 3);
+        assert(ym2.index()   == 3);
+        assert(ym1 == ym2);
+    }
+    }
+
+    {   // year_month_weekday + years (and switched)
+    ASSERT_NOEXCEPT(std::declval<year_month_weekday>() + std::declval<years>());
+    ASSERT_NOEXCEPT(std::declval<years>() + std::declval<year_month_weekday>());
+
+    ASSERT_SAME_TYPE(year_month_weekday, decltype(std::declval<year_month_weekday>() + std::declval<years>()));
+    ASSERT_SAME_TYPE(year_month_weekday, decltype(std::declval<years>() + std::declval<year_month_weekday>()));
+    
+    static_assert(testConstexprYears (year_month_weekday{year{1}, January, weekday_indexed{Tuesday, 1}}), "");
+
+    year_month_weekday ym{year{1234}, std::chrono::January, weekday_indexed{Tuesday, 3}};
+    for (int i = 0; i <= 10; ++i)
+    {
+        year_month_weekday ym1 = ym + years{i};
+        year_month_weekday ym2 = years{i} + ym;
+        assert(static_cast<int>(ym1.year()) == i + 1234);
+        assert(static_cast<int>(ym2.year()) == i + 1234);
+        assert(ym1.month()   == January);
+        assert(ym2.month()   == January);
+        assert(ym1.weekday() == Tuesday);
+        assert(ym2.weekday() == Tuesday);
+        assert(ym1.index()   == 3);
+        assert(ym2.index()   == 3);
+        assert(ym1 == ym2);
+    }
+    }
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..da000744e
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/time.cal.ymwd.nonmembers/streaming.pass.cpp
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_weekday;
+
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const year_month_weekday& ym);
+// 
+// Returns: os << ym.year() << '/' << ym.month().
+// 
+// 
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     to_stream(basic_ostream<charT, traits>& os, const charT* fmt, const year_month_weekday& ym);
+// 
+// Effects: Streams ym into os using the format specified by the NTCTS fmt. fmt encoding follows the rules specified in 25.11.
+// 
+// template<class charT, class traits, class Alloc = allocator<charT>>
+//     basic_istream<charT, traits>&
+//   from_stream(basic_istream<charT, traits>& is, const charT* fmt,
+//               year_month_weekday& ym, basic_string<charT, traits, Alloc>* abbrev = nullptr,
+//               minutes* offset = nullptr);
+// 
+// Effects: Attempts to parse the input stream is into the year_month_weekday ym using the format 
+//         flags given in the NTCTS fmt as specified in 25.12. If the parse fails to decode
+//         a valid year_month_weekday, is.setstate(ios_- base::failbit) shall be called and ym shall
+//         not be modified. If %Z is used and successfully parsed, that value will be assigned
+//         to *abbrev if abbrev is non-null. If %z (or a modified variant) is used and 
+//         successfully parsed, that value will be assigned to *offset if offset is non-null.
+
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+#include "test_macros.h"
+
+int main()
+{
+    using year_month_weekday = std::chrono::year_month_weekday;
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using weekday             = std::chrono::weekday;
+    
+    std::cout << year_month_weekday{year{2018}, month{3}, weekday{4}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwd/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwd/types.pass.cpp
new file mode 100644
index 000000000..cd7a0b997
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwd/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year_month_weekday = std::chrono::year_month_weekday;
+    
+    static_assert(std::is_trivially_copyable_v<year_month_weekday>, "");
+    static_assert(std::is_standard_layout_v<year_month_weekday>, "");
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/ctor.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/ctor.pass.cpp
new file mode 100644
index 000000000..2bc4038cd
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/ctor.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+//  constexpr year_month_weekday_last(const chrono::year& y, const chrono::month& m,
+//                               const chrono::weekday_last& wdl) noexcept;
+//
+//  Effects:  Constructs an object of type year_month_weekday_last by initializing
+//                y_ with y, m_ with m, and wdl_ with wdl.
+//
+//  constexpr chrono::year                 year() const noexcept;
+//  constexpr chrono::month               month() const noexcept;
+//  constexpr chrono::weekday           weekday() const noexcept;
+//  constexpr chrono::weekday_last weekday_last() const noexcept;
+//  constexpr bool                           ok() const noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+
+    constexpr month January = std::chrono::January;
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+
+    ASSERT_NOEXCEPT(year_month_weekday_last{year{1}, month{1}, weekday_last{Tuesday}});
+    
+    constexpr year_month_weekday_last ym1{year{2019}, January, weekday_last{Tuesday}};
+    static_assert( ym1.year()         == year{2019},            "");
+    static_assert( ym1.month()        == January,               "");
+    static_assert( ym1.weekday()      == Tuesday,               "");
+    static_assert( ym1.weekday_last() == weekday_last{Tuesday}, "");
+    static_assert( ym1.ok(),                                    "");
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/month.pass.cpp
new file mode 100644
index 000000000..5602d259d
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/month.pass.cpp
@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+// constexpr chrono::month month() const noexcept;
+//  Returns: wd_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+
+    ASSERT_NOEXCEPT(                 std::declval<const year_month_weekday_last>().month());
+    ASSERT_SAME_TYPE(month, decltype(std::declval<const year_month_weekday_last>().month()));
+
+    static_assert( year_month_weekday_last{year{}, month{}, weekday_last{weekday{}}}.month() == month{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month_weekday_last ymd(year{1234}, month{i}, weekday_last{weekday{}});
+        assert( static_cast<unsigned>(ymd.month()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/ok.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/ok.pass.cpp
new file mode 100644
index 000000000..2c431848e
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/ok.pass.cpp
@@ -0,0 +1,73 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+// constexpr bool ok() const noexcept;
+//  Returns: y_.ok() && m_.ok() && wdl_.ok().
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+
+    constexpr month January   = std::chrono::January;
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+
+    ASSERT_NOEXCEPT(                std::declval<const year_month_weekday_last>().ok());
+    ASSERT_SAME_TYPE(bool, decltype(std::declval<const year_month_weekday_last>().ok()));
+
+    static_assert(!year_month_weekday_last{year{-32768}, month{}, weekday_last{weekday{}}}.ok(),  ""); // All three bad
+
+    static_assert(!year_month_weekday_last{year{-32768}, January, weekday_last{Tuesday}}.ok(),    ""); // Bad year
+    static_assert(!year_month_weekday_last{year{2019},   month{}, weekday_last{Tuesday}}.ok(),    ""); // Bad month
+    static_assert(!year_month_weekday_last{year{2019},   January, weekday_last{weekday{7}}}.ok(), ""); // Bad day
+
+    static_assert(!year_month_weekday_last{year{-32768}, month{}, weekday_last{Tuesday}}.ok(),    ""); // Bad year & month
+    static_assert(!year_month_weekday_last{year{2019},   month{}, weekday_last{weekday{7}}}.ok(), ""); // Bad month & day
+    static_assert(!year_month_weekday_last{year{-32768}, January, weekday_last{weekday{7}}}.ok(), ""); // Bad year & day
+
+    static_assert( year_month_weekday_last{year{2019},   January, weekday_last{Tuesday}}.ok(),    ""); // All OK
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        year_month_weekday_last ym{year{2019}, January, weekday_last{Tuesday}};
+        assert((ym.ok() == weekday_last{Tuesday}.ok()));
+    }
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        year_month_weekday_last ym{year{2019}, January, weekday_last{weekday{i}}};
+        assert((ym.ok() == weekday_last{weekday{i}}.ok()));
+    }
+
+    for (unsigned i = 0; i <= 50; ++i)
+    {
+        year_month_weekday_last ym{year{2019}, month{i}, weekday_last{Tuesday}};
+        assert((ym.ok() == month{i}.ok()));
+    }
+
+    const int ymax = static_cast<int>(year::max());
+    for (int i = ymax - 100; i <= ymax + 100; ++i)
+    {
+        year_month_weekday_last ym{year{i}, January, weekday_last{Tuesday}};
+        assert((ym.ok() == year{i}.ok()));
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/op_local_days.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/op_local_days.pass.cpp
new file mode 100644
index 000000000..48b87cbd8
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/op_local_days.pass.cpp
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr operator local_days() const noexcept;
+//  Returns: local_days{sys_days{*this}.time_since_epoch()}.
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+    using sys_days            = std::chrono::local_days;
+
+    ASSERT_NOEXCEPT(                static_cast<local_days>(std::declval<const year_month_day_last>().year()));
+    ASSERT_SAME_TYPE(year, decltype(static_cast<local_days>(std::declval<const year_month_day_last>().year()));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/op_sys_days.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/op_sys_days.pass.cpp
new file mode 100644
index 000000000..a89f71fae
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/op_sys_days.pass.cpp
@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_day_last;
+
+// constexpr operator sys_days() const noexcept;
+//  Returns: sys_days{year()/month()/day()}.
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                = std::chrono::year;
+    using month               = std::chrono::month;
+    using day                 = std::chrono::day;
+    using month_day_last      = std::chrono::month_day_last;
+    using year_month_day_last = std::chrono::year_month_day_last;
+    using sys_days            = std::chrono::sys_days;
+
+    ASSERT_NOEXCEPT(                static_cast<sys_days>(std::declval<const year_month_day_last>().year()));
+    ASSERT_SAME_TYPE(year, decltype(static_cast<sys_days>(std::declval<const year_month_day_last>().year()));
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/plus_minus_equal_month.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/plus_minus_equal_month.pass.cpp
new file mode 100644
index 000000000..0785befc2
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/plus_minus_equal_month.pass.cpp
@@ -0,0 +1,75 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+// constexpr year_month_weekday_last& operator+=(const months& m) noexcept;
+// constexpr year_month_weekday_last& operator-=(const months& m) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr(D d1)
+{
+    if (static_cast<unsigned>((d1          ).month()) !=  1) return false;
+    if (static_cast<unsigned>((d1 += Ds{ 1}).month()) !=  2) return false;
+    if (static_cast<unsigned>((d1 += Ds{ 2}).month()) !=  4) return false;
+    if (static_cast<unsigned>((d1 += Ds{12}).month()) !=  4) return false;
+    if (static_cast<unsigned>((d1 -= Ds{ 1}).month()) !=  3) return false;
+    if (static_cast<unsigned>((d1 -= Ds{ 2}).month()) !=  1) return false;
+    if (static_cast<unsigned>((d1 -= Ds{12}).month()) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+    using months                  = std::chrono::months;
+
+    ASSERT_NOEXCEPT(std::declval<year_month_weekday_last&>() += std::declval<months>());
+    ASSERT_NOEXCEPT(std::declval<year_month_weekday_last&>() -= std::declval<months>());
+
+    ASSERT_SAME_TYPE(year_month_weekday_last&, decltype(std::declval<year_month_weekday_last&>() += std::declval<months>()));
+    ASSERT_SAME_TYPE(year_month_weekday_last&, decltype(std::declval<year_month_weekday_last&>() -= std::declval<months>()));
+
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    static_assert(testConstexpr<year_month_weekday_last, months>(year_month_weekday_last{year{1234}, month{1}, weekday_last{Tuesday}}), "");
+
+    for (unsigned i = 0; i <= 10; ++i)
+    {
+        year y{1234};
+        year_month_weekday_last ymwd(y, month{i}, weekday_last{Tuesday});
+
+        assert(static_cast<unsigned>((ymwd += months{2}).month()) == i + 2);
+        assert(ymwd.year()     == y);
+        assert(ymwd.weekday()  == Tuesday);
+
+        assert(static_cast<unsigned>((ymwd             ).month()) == i + 2);
+        assert(ymwd.year()     == y);
+        assert(ymwd.weekday()  == Tuesday);
+
+        assert(static_cast<unsigned>((ymwd -= months{1}).month()) == i + 1);
+        assert(ymwd.year()     == y);
+        assert(ymwd.weekday()  == Tuesday);
+
+        assert(static_cast<unsigned>((ymwd             ).month()) == i + 1);
+        assert(ymwd.year()     == y);
+        assert(ymwd.weekday()  == Tuesday);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/plus_minus_equal_year.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/plus_minus_equal_year.pass.cpp
new file mode 100644
index 000000000..3a2a70009
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/plus_minus_equal_year.pass.cpp
@@ -0,0 +1,76 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+// constexpr year_month_weekday_last& operator+=(const years& d) noexcept;
+// constexpr year_month_weekday_last& operator-=(const years& d) noexcept;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename D, typename Ds>
+constexpr bool testConstexpr(D d1)
+{
+    if (static_cast<int>((d1          ).year()) !=  1) return false;
+    if (static_cast<int>((d1 += Ds{ 1}).year()) !=  2) return false;
+    if (static_cast<int>((d1 += Ds{ 2}).year()) !=  4) return false;
+    if (static_cast<int>((d1 += Ds{12}).year()) != 16) return false;
+    if (static_cast<int>((d1 -= Ds{ 1}).year()) != 15) return false;
+    if (static_cast<int>((d1 -= Ds{ 2}).year()) != 13) return false;
+    if (static_cast<int>((d1 -= Ds{12}).year()) !=  1) return false;
+    return true;
+}
+
+int main()
+{
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+    using years                   = std::chrono::years;
+
+    ASSERT_NOEXCEPT(std::declval<year_month_weekday_last&>() += std::declval<years>());
+    ASSERT_NOEXCEPT(std::declval<year_month_weekday_last&>() -= std::declval<years>());
+
+    ASSERT_SAME_TYPE(year_month_weekday_last&, decltype(std::declval<year_month_weekday_last&>() += std::declval<years>()));
+    ASSERT_SAME_TYPE(year_month_weekday_last&, decltype(std::declval<year_month_weekday_last&>() -= std::declval<years>()));
+    
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    constexpr month January = std::chrono::January;
+
+    static_assert(testConstexpr<year_month_weekday_last, years>(year_month_weekday_last{year{1}, January, weekday_last{Tuesday}}), "");
+
+    for (int i = 1000; i <= 1010; ++i)
+    {
+        year_month_weekday_last ymwd(year{i}, January, weekday_last{Tuesday});
+
+        assert(static_cast<int>((ymwd += years{2}).year()) == i + 2);
+        assert(ymwd.month()    == January);
+        assert(ymwd.weekday()  == Tuesday);
+
+        assert(static_cast<int>((ymwd            ).year()) == i + 2);
+        assert(ymwd.month()    == January);
+        assert(ymwd.weekday()  == Tuesday);
+
+        assert(static_cast<int>((ymwd -= years{1}).year()) == i + 1);
+        assert(ymwd.month()    == January);
+        assert(ymwd.weekday()  == Tuesday);
+
+        assert(static_cast<int>((ymwd            ).year()) == i + 1);
+        assert(ymwd.month()    == January);
+        assert(ymwd.weekday()  == Tuesday);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/weekday.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/weekday.pass.cpp
new file mode 100644
index 000000000..a88257677
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/weekday.pass.cpp
@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+// constexpr chrono::weekday weekday() const noexcept;
+//  Returns: wdi_.weekday()
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+
+    ASSERT_NOEXCEPT(                   std::declval<const year_month_weekday_last>().weekday());
+    ASSERT_SAME_TYPE(weekday, decltype(std::declval<const year_month_weekday_last>().weekday()));
+
+    static_assert( year_month_weekday_last{year{}, month{}, weekday_last{weekday{}}}.weekday() == weekday{}, "");
+
+    for (unsigned i = 1; i <= 50; ++i)
+    {
+        year_month_weekday_last ymwdl(year{1}, month{1}, weekday_last{weekday{i}});
+        assert(static_cast<unsigned>(ymwdl.weekday()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/year.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/year.pass.cpp
new file mode 100644
index 000000000..86e2985b4
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.members/year.pass.cpp
@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+// constexpr chrono::year year() const noexcept;
+//  Returns: d_
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+
+    ASSERT_NOEXCEPT(                std::declval<const year_month_weekday_last>().year());
+    ASSERT_SAME_TYPE(year, decltype(std::declval<const year_month_weekday_last>().year()));
+
+    static_assert( year_month_weekday_last{year{}, month{}, weekday_last{weekday{}}}.year() == year{}, "");
+
+    for (int i = 1; i <= 50; ++i)
+    {
+        year_month_weekday_last ymwdl(year{i}, month{1}, weekday_last{weekday{}});
+        assert(static_cast<int>(ymwdl.year()) == i);
+    }
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/comparisons.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/comparisons.pass.cpp
new file mode 100644
index 000000000..4ddfed6f1
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/comparisons.pass.cpp
@@ -0,0 +1,114 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+// constexpr bool operator==(const year_month_weekday_last& x, const year_month_weekday_last& y) noexcept;
+//   Returns: x.year() == y.year() && x.month() == y.month() && x.weekday_last() == y.weekday_last()
+//
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_comparisons.h"
+
+int main()
+{
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+
+    AssertComparisons2AreNoexcept<year_month_weekday_last>();
+    AssertComparisons2ReturnBool<year_month_weekday_last>();
+    
+    constexpr month January   = std::chrono::January;
+    constexpr month February  = std::chrono::February;
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    constexpr weekday Wednesday = std::chrono::Wednesday;
+
+    static_assert( testComparisons2(
+        year_month_weekday_last{year{1234}, January, weekday_last{Tuesday}}, 
+        year_month_weekday_last{year{1234}, January, weekday_last{Tuesday}},
+        true), "");
+    
+//  different day
+    static_assert( testComparisons2(
+        year_month_weekday_last{year{1234}, January, weekday_last{Tuesday}}, 
+        year_month_weekday_last{year{1234}, January, weekday_last{Wednesday}},
+        false), "");
+    
+//  different month
+    static_assert( testComparisons2(
+        year_month_weekday_last{year{1234}, January,  weekday_last{Tuesday}},
+        year_month_weekday_last{year{1234}, February, weekday_last{Tuesday}},
+        false), "");
+
+//  different year
+    static_assert( testComparisons2(
+        year_month_weekday_last{year{1234}, January, weekday_last{Tuesday}},
+        year_month_weekday_last{year{1235}, January, weekday_last{Tuesday}},
+        false), "");
+
+
+//  different month and day
+    static_assert( testComparisons2(
+        year_month_weekday_last{year{1234}, January,  weekday_last{Tuesday}},
+        year_month_weekday_last{year{1234}, February, weekday_last{Wednesday}},
+        false), "");
+
+//  different year and month
+    static_assert( testComparisons2(
+        year_month_weekday_last{year{1234}, February, weekday_last{Tuesday}},
+        year_month_weekday_last{year{1235}, January,  weekday_last{Tuesday}},
+        false), "");
+
+//  different year and day
+    static_assert( testComparisons2(
+        year_month_weekday_last{year{1234}, January, weekday_last{Wednesday}},
+        year_month_weekday_last{year{1235}, January, weekday_last{Tuesday}},
+        false), "");
+
+//  different year, month and day
+    static_assert( testComparisons2(
+        year_month_weekday_last{year{1234}, February, weekday_last{Wednesday}},
+        year_month_weekday_last{year{1235}, January,  weekday_last{Tuesday}},
+        false), "");
+
+
+//  same year, different days
+    for (unsigned i = 1; i < 28; ++i)
+        for (unsigned j = 1; j < 28; ++j)
+            assert((testComparisons2(
+                year_month_weekday_last{year{1234}, January, weekday_last{weekday{i}}},
+                year_month_weekday_last{year{1234}, January, weekday_last{weekday{j}}},
+                i == j)));
+    
+//  same year, different months
+    for (unsigned i = 1; i < 12; ++i)
+        for (unsigned j = 1; j < 12; ++j)
+            assert((testComparisons2(
+                year_month_weekday_last{year{1234}, month{i}, weekday_last{Tuesday}},
+                year_month_weekday_last{year{1234}, month{j}, weekday_last{Tuesday}},
+                i == j)));
+    
+//  same month, different years
+    for (int i = 1000; i < 20; ++i)
+        for (int j = 1000; j < 20; ++j)
+        assert((testComparisons2(
+            year_month_weekday_last{year{i}, January, weekday_last{Tuesday}},
+            year_month_weekday_last{year{j}, January, weekday_last{Tuesday}},
+            i == j)));
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/minus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/minus.pass.cpp
new file mode 100644
index 000000000..2b58c03ef
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/minus.pass.cpp
@@ -0,0 +1,93 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+// constexpr year_month_weekday_last operator-(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
+//   Returns: ymwdl + (-dm).
+// 
+// constexpr year_month_weekday_last operator-(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
+//   Returns: ymwdl + (-dy).
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+#include <iostream>
+
+constexpr bool testConstexprYears(std::chrono::year_month_weekday_last ym)
+{
+    std::chrono::years offset{14};
+    if (static_cast<int>((ym         ).year()) != 66) return false;
+    if (static_cast<int>((ym - offset).year()) != 52) return false;
+    return true;
+}
+
+constexpr bool testConstexprMonths(std::chrono::year_month_weekday_last ym)
+{
+    std::chrono::months offset{6};
+    if (static_cast<unsigned>((ym         ).month()) != 10) return false;
+    if (static_cast<unsigned>((ym - offset).month()) !=  4) return false;
+    return true;
+}
+
+int main()
+{
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+    using years                   = std::chrono::years;
+    using months                  = std::chrono::months;
+
+    constexpr month October = std::chrono::October;
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+
+    { // year_month_weekday_last - years
+
+    ASSERT_NOEXCEPT(                                   std::declval<year_month_weekday_last>() - std::declval<years>());
+    ASSERT_SAME_TYPE(year_month_weekday_last, decltype(std::declval<year_month_weekday_last>() - std::declval<years>()));
+
+    static_assert(testConstexprYears(year_month_weekday_last{year{66}, October, weekday_last{Tuesday}}), "");
+
+    year_month_weekday_last ym{year{1234}, October, weekday_last{Tuesday}};
+    for (int i = 0; i <= 10; ++i)
+    {
+        year_month_weekday_last ym1 = ym - years{i};
+        assert(ym1.year()         == year{1234 - i});
+        assert(ym1.month()        == October);
+        assert(ym1.weekday()      == Tuesday);
+        assert(ym1.weekday_last() == weekday_last{Tuesday});
+    }
+    }
+    
+    { // year_month_weekday_last - months
+
+    ASSERT_NOEXCEPT(                                   std::declval<year_month_weekday_last>() - std::declval<months>());
+    ASSERT_SAME_TYPE(year_month_weekday_last, decltype(std::declval<year_month_weekday_last>() - std::declval<months>()));
+
+    static_assert(testConstexprMonths(year_month_weekday_last{year{66}, October, weekday_last{Tuesday}}), "");
+
+    year_month_weekday_last ym{year{1234}, October, weekday_last{Tuesday}};
+    for (unsigned i = 0; i < 10; ++i)
+    {
+        year_month_weekday_last ym1 = ym - months{i};
+        assert(ym1.year()         == year{1234});
+        assert(ym1.month()        == month{10 - i});
+        assert(ym1.weekday()      == Tuesday);
+        assert(ym1.weekday_last() == weekday_last{Tuesday});
+    }
+    }
+    
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/plus.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/plus.pass.cpp
new file mode 100644
index 000000000..59ae592a0
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/plus.pass.cpp
@@ -0,0 +1,116 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last;
+
+// constexpr year_month_weekday_last operator+(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
+//   Returns: (ymwdl.year() / ymwdl.month() + dm) / ymwdl.weekday_last().
+// 
+// constexpr year_month_weekday_last operator+(const months& dm, const year_month_weekday_last& ymwdl) noexcept;
+//   Returns: ymwdl + dm.
+// 
+// constexpr year_month_weekday_last operator+(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
+//   Returns: {ymwdl.year()+dy, ymwdl.month(), ymwdl.weekday_last()}.
+// 
+// constexpr year_month_weekday_last operator+(const years& dy, const year_month_weekday_last& ymwdl) noexcept;
+//   Returns: ymwdl + dy.
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool testConstexprYears(std::chrono::year_month_weekday_last ym)
+{
+    std::chrono::years offset{23};
+    if (static_cast<int>((ym         ).year()) !=  1) return false;
+    if (static_cast<int>((ym + offset).year()) != 24) return false;
+    if (static_cast<int>((offset + ym).year()) != 24) return false;
+    return true;
+}
+
+constexpr bool testConstexprMonths(std::chrono::year_month_weekday_last ym)
+{
+    std::chrono::months offset{6};
+    if (static_cast<unsigned>((ym         ).month()) !=  1) return false;
+    if (static_cast<unsigned>((ym + offset).month()) !=  7) return false;
+    if (static_cast<unsigned>((offset + ym).month()) !=  7) return false;
+    return true;
+}
+
+
+int main()
+{
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+    using years                   = std::chrono::years;
+    using months                  = std::chrono::months;
+
+    constexpr weekday Tuesday = std::chrono::Tuesday;
+    constexpr month January = std::chrono::January;
+
+    {   // year_month_weekday_last + months
+    ASSERT_NOEXCEPT(std::declval<year_month_weekday_last>() + std::declval<months>());
+    ASSERT_NOEXCEPT(std::declval<months>() + std::declval<year_month_weekday_last>());
+
+    ASSERT_SAME_TYPE(year_month_weekday_last, decltype(std::declval<year_month_weekday_last>() + std::declval<months>()));
+    ASSERT_SAME_TYPE(year_month_weekday_last, decltype(std::declval<months>() + std::declval<year_month_weekday_last>()));
+
+    static_assert(testConstexprMonths(year_month_weekday_last{year{1}, January, weekday_last{Tuesday}}), "");
+
+    year_month_weekday_last ym{year{1234}, January, weekday_last{Tuesday}};
+    for (int i = 0; i <= 10; ++i)  // TODO test wrap-around
+    {
+        year_month_weekday_last ym1 = ym + months{i};
+        year_month_weekday_last ym2 = months{i} + ym;
+        assert(ym1.year()         == year(1234));
+        assert(ym2.year()         == year(1234));
+        assert(ym1.month()        == month(1 + i));
+        assert(ym2.month()        == month(1 + i));
+        assert(ym1.weekday()      == Tuesday);
+        assert(ym2.weekday()      == Tuesday);
+        assert(ym1.weekday_last() == weekday_last{Tuesday});
+        assert(ym2.weekday_last() == weekday_last{Tuesday});
+        assert(ym1 == ym2);
+    }
+    }
+
+    {   // year_month_weekday_last + years
+    ASSERT_NOEXCEPT(std::declval<year_month_weekday_last>() + std::declval<years>());
+    ASSERT_NOEXCEPT(std::declval<years>() + std::declval<year_month_weekday_last>());
+
+    ASSERT_SAME_TYPE(year_month_weekday_last, decltype(std::declval<year_month_weekday_last>() + std::declval<years>()));
+    ASSERT_SAME_TYPE(year_month_weekday_last, decltype(std::declval<years>() + std::declval<year_month_weekday_last>()));
+    
+    static_assert(testConstexprYears (year_month_weekday_last{year{1}, January, weekday_last{Tuesday}}), "");
+
+    year_month_weekday_last ym{year{1234}, std::chrono::January, weekday_last{Tuesday}};
+    for (int i = 0; i <= 10; ++i)
+    {
+        year_month_weekday_last ym1 = ym + years{i};
+        year_month_weekday_last ym2 = years{i} + ym;
+        assert(ym1.year()         == year(1234 + i));
+        assert(ym2.year()         == year(1234 + i));
+        assert(ym1.month()        == January);
+        assert(ym2.month()        == January);
+        assert(ym1.weekday()      == Tuesday);
+        assert(ym2.weekday()      == Tuesday);
+        assert(ym1.weekday_last() == weekday_last{Tuesday});
+        assert(ym2.weekday_last() == weekday_last{Tuesday});
+        assert(ym1 == ym2);
+    }
+    }
+
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/streaming.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/streaming.pass.cpp
new file mode 100644
index 000000000..d23cb3cf1
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/time.cal.ymwdlast.nonmembers/streaming.pass.cpp
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// XFAIL: *
+
+// <chrono>
+// class year_month_weekday_last;
+
+// template<class charT, class traits>
+//     basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const year_month_weekday_last& ymwdl);
+// 
+//   Returns: os << ymwdl.year() << '/' << ymwdl.month() << '/' << ymwdl.weekday_last().
+
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+#include <iostream>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+    using year                    = std::chrono::year;
+    using month                   = std::chrono::month;
+    using weekday                 = std::chrono::weekday;
+    using weekday_last            = std::chrono::weekday_last;
+    
+    std::cout << year_month_weekday_last{year{2018}, month{3}, weekday_last{weekday{4}}};
+}
diff --git a/test/std/utilities/time/time.cal/time.cal.ymwdlast/types.pass.cpp b/test/std/utilities/time/time.cal/time.cal.ymwdlast/types.pass.cpp
new file mode 100644
index 000000000..198af651f
--- /dev/null
+++ b/test/std/utilities/time/time.cal/time.cal.ymwdlast/types.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+// class year_month_weekday_last_last;
+
+#include <chrono>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    using year_month_weekday_last = std::chrono::year_month_weekday_last;
+    
+    static_assert(std::is_trivially_copyable_v<year_month_weekday_last>, "");
+    static_assert(std::is_standard_layout_v<year_month_weekday_last>, "");
+}
diff --git a/test/std/utilities/time/time.duration/time.duration.literals/literals.pass.cpp b/test/std/utilities/time/time.duration/time.duration.literals/literals.pass.cpp
index d5c0207c0..e10b35efb 100644
--- a/test/std/utilities/time/time.duration/time.duration.literals/literals.pass.cpp
+++ b/test/std/utilities/time/time.duration/time.duration.literals/literals.pass.cpp
@@ -14,6 +14,8 @@
 #include <type_traits>
 #include <cassert>
 
+#include "test_macros.h"
+
 int main()
 {
     using namespace std::literals::chrono_literals;
@@ -55,4 +57,5 @@ int main()
     assert ( ns == std::chrono::nanoseconds(645));
     auto ns2 = 645.ns;
     assert ( ns == ns2 );
+
 }
diff --git a/test/std/utilities/time/time.duration/time.duration.literals/literals1.pass.cpp b/test/std/utilities/time/time.duration/time.duration.literals/literals1.pass.cpp
index 5e59e1153..6e43e3a9a 100644
--- a/test/std/utilities/time/time.duration/time.duration.literals/literals1.pass.cpp
+++ b/test/std/utilities/time/time.duration/time.duration.literals/literals1.pass.cpp
@@ -7,8 +7,8 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-
 // UNSUPPORTED: c++98, c++03, c++11
+
 #include <chrono>
 #include <cassert>
 
@@ -45,4 +45,27 @@ int main()
     assert ( ns == nanoseconds(645));
     auto ns2 = 645.ns;
     assert ( ns == ns2 );
+
+#if TEST_STD_VER > 17
+    assert(Sunday    == weekday(0));
+    assert(Monday    == weekday(1));
+    assert(Tuesday   == weekday(2));
+    assert(Wednesday == weekday(3));
+    assert(Thursday  == weekday(4));
+    assert(Friday    == weekday(5));
+    assert(Saturday  == weekday(6));
+
+    assert(January   == month(1));
+    assert(February  == month(2));
+    assert(March     == month(3));
+    assert(April     == month(4));
+    assert(May       == month(5));
+    assert(June      == month(6));
+    assert(July      == month(7));
+    assert(August    == month(8));
+    assert(September == month(9));
+    assert(October   == month(10));
+    assert(November  == month(11));
+    assert(December  == month(12));
+#endif
 }
diff --git a/test/std/utilities/time/weeks.pass.cpp b/test/std/utilities/time/weeks.pass.cpp
new file mode 100644
index 000000000..6099d55b7
--- /dev/null
+++ b/test/std/utilities/time/weeks.pass.cpp
@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// using weeks = duration<signed integer type of at least 22 bits, ratio_multiply<ratio<7>, days::period>>;
+
+#include <chrono>
+#include <type_traits>
+#include <limits>
+
+int main()
+{
+    typedef std::chrono::weeks D;
+    typedef D::rep Rep;
+    typedef D::period Period;
+    static_assert(std::is_signed<Rep>::value, "");
+    static_assert(std::is_integral<Rep>::value, "");
+    static_assert(std::numeric_limits<Rep>::digits >= 22, "");
+    static_assert(std::is_same_v<Period, std::ratio_multiply<std::ratio<7>, std::chrono::days::period>>, "");
+}
diff --git a/test/std/utilities/time/years.pass.cpp b/test/std/utilities/time/years.pass.cpp
new file mode 100644
index 000000000..ad68e648a
--- /dev/null
+++ b/test/std/utilities/time/years.pass.cpp
@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// using years = duration<signed integer type of at least 17 bits, ratio_multiply<ratio<146097, 400>, days::period>>
+
+#include <chrono>
+#include <type_traits>
+#include <limits>
+
+int main()
+{
+    typedef std::chrono::years D;
+    typedef D::rep Rep;
+    typedef D::period Period;
+    static_assert(std::is_signed<Rep>::value, "");
+    static_assert(std::is_integral<Rep>::value, "");
+    static_assert(std::numeric_limits<Rep>::digits >= 17, "");
+    static_assert(std::is_same_v<Period, std::ratio_multiply<std::ratio<146097, 400>, std::chrono::days::period>>, "");
+}