From f1f54dc0fbe3da97487c96f3e183fb9378822d5e Mon Sep 17 00:00:00 2001
From: Marshall Clow <mclow.lists@gmail.com>
Date: Wed, 18 Jul 2018 17:37:51 +0000
Subject: [PATCH] Update the synopsis for <chrono> for C++20. No functional
 change.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@337406 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/chrono | 492 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 492 insertions(+)

diff --git a/include/chrono b/include/chrono
index 809f773b6..f6a6f4b24 100644
--- a/include/chrono
+++ b/include/chrono
@@ -147,6 +147,11 @@ template <class Clock, class Duration1, class Duration2>
 
 namespace chrono {
 
+
+template<class T> struct is_clock;  // C++20
+template<class T> inline constexpr bool is_clock_v = is_clock<T>::value;   // C++20
+
+
 // duration arithmetic
 template <class Rep1, class Period1, class Rep2, class Period2>
   constexpr
@@ -204,6 +209,8 @@ template <class ToDuration, class Rep, class Period>
 template <class ToDuration, class Rep, class Period>
     constexpr ToDuration round(const duration<Rep, Period>& d);    // C++17
 
+// duration I/O is elsewhere
+
 // time_point arithmetic (all constexpr in C++14)
 template <class Clock, class Duration1, class Rep2, class Period2>
   time_point<Clock, typename common_type<Duration1, duration<Rep2, Period2>>::type>
@@ -251,6 +258,7 @@ template <class ToDuration, class Clock, class Duration>
 
 template <class Rep, class Period>
     constexpr duration<Rep, Period> abs(duration<Rep, Period> d);  // C++17
+
 // Clocks
 
 class system_clock
@@ -267,6 +275,28 @@ public:
     static time_point from_time_t(time_t __t) noexcept;
 };
 
+template <class Duration>
+  using sys_time  = time_point<system_clock, Duration>; // C++20
+using sys_seconds = sys_time<seconds>;                  // C++20
+using sys_days    = sys_time<days>;                     // C++20
+
+class utc_clock;                                        // C++20
+
+template <class Duration>
+  using utc_time  = time_point<utc_clock, Duration>;    // C++20
+using utc_seconds = utc_time<seconds>;                  // C++20
+
+class tai_clock;                                        // C++20
+
+template <class Duration>
+  using tai_time  = time_point<tai_clock, Duration>;    // C++20
+using tai_seconds = tai_time<seconds>;                  // C++20
+
+class file_clock;                                       // C++20
+
+template<class Duration>
+  using file_time = time_point<file_clock, Duration>;   // C++20
+
 class steady_clock
 {
 public:
@@ -281,8 +311,466 @@ public:
 
 typedef steady_clock high_resolution_clock;
 
+// 25.7.8, local time           // C++20
+struct local_t {};
+template<class Duration>
+  using local_time  = time_point<local_t, Duration>;
+using local_seconds = local_time<seconds>;
+using local_days    = local_time<days>;
+
+// 25.7.9, time_point conversions template<class DestClock, class SourceClock>    // C++20
+struct clock_time_conversion;
+
+template<class DestClock, class SourceClock, class Duration>
+  auto clock_cast(const time_point<SourceClock, Duration>& t);
+  
+// 25.8.2, class last_spec    // C++20
+struct last_spec;
+
+// 25.8.3, class day          // C++20
+
+class day;
+constexpr bool operator==(const day& x, const day& y) noexcept;
+constexpr bool operator!=(const day& x, const day& y) noexcept;
+constexpr bool operator< (const day& x, const day& y) noexcept;
+constexpr bool operator> (const day& x, const day& y) noexcept;
+constexpr bool operator<=(const day& x, const day& y) noexcept;
+constexpr bool operator>=(const day& x, const day& y) noexcept;
+constexpr day  operator+(const day&  x, const days& y) noexcept;
+constexpr day  operator+(const days& x, const day&  y) noexcept;
+constexpr day  operator-(const day&  x, const days& y) noexcept;
+constexpr days operator-(const day&  x, const day&  y) noexcept;
+
+// 25.8.4, class month    // C++20
+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;
+constexpr month  operator+(const month&  x, const months& y) noexcept;
+constexpr month  operator+(const months& x,  const month& y) noexcept;
+constexpr month  operator-(const month&  x, const months& y) noexcept;
+constexpr months operator-(const month&  x,  const month& y) noexcept;
+
+// 25.8.5, class year    // C++20
+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;
+constexpr year  operator+(const year&  x, const years& y) noexcept;
+constexpr year  operator+(const years& x, const year&  y) noexcept;
+constexpr year  operator-(const year&  x, const years& y) noexcept;
+constexpr years operator-(const year&  x, const year&  y) noexcept;
+
+// 25.8.6, class weekday    // C++20
+class weekday;
+
+constexpr bool operator==(const weekday& x, const weekday& y) noexcept;
+constexpr bool operator!=(const weekday& x, const weekday& y) noexcept;
+constexpr weekday operator+(const weekday& x, const days&    y) noexcept;
+constexpr weekday operator+(const days&    x, const weekday& y) noexcept;
+constexpr weekday operator-(const weekday& x, const days&    y) noexcept;
+constexpr days    operator-(const weekday& x, const weekday& y) noexcept;
+
+// 25.8.7, class weekday_indexed    // C++20
+
+class weekday_indexed;
+constexpr bool operator==(const weekday_indexed& x, const weekday_indexed& y) noexcept;
+constexpr bool operator!=(const weekday_indexed& x, const weekday_indexed& y) noexcept;
+
+// 25.8.8, class weekday_last    // C++20
+class weekday_last;
+
+constexpr bool operator==(const weekday_last& x, const weekday_last& y) noexcept;
+constexpr bool operator!=(const weekday_last& x, const weekday_last& y) noexcept;
+
+// 25.8.9, class month_day    // C++20
+class month_day;
+
+constexpr bool operator==(const month_day& x, const month_day& y) noexcept;
+constexpr bool operator!=(const month_day& x, const month_day& y) noexcept;
+constexpr bool operator< (const month_day& x, const month_day& y) noexcept;
+constexpr bool operator> (const month_day& x, const month_day& y) noexcept;
+constexpr bool operator<=(const month_day& x, const month_day& y) noexcept;
+constexpr bool operator>=(const month_day& x, const month_day& y) noexcept;
+
+
+// 25.8.10, class month_day_last    // C++20
+class month_day_last;
+
+constexpr bool operator==(const month_day_last& x, const month_day_last& y) noexcept;
+constexpr bool operator!=(const month_day_last& x, const month_day_last& y) noexcept;
+constexpr bool operator< (const month_day_last& x, const month_day_last& y) noexcept;
+constexpr bool operator> (const month_day_last& x, const month_day_last& y) noexcept;
+constexpr bool operator<=(const month_day_last& x, const month_day_last& y) noexcept;
+constexpr bool operator>=(const month_day_last& x, const month_day_last& y) noexcept;
+
+// 25.8.11, class month_weekday    // C++20
+class month_weekday;
+
+constexpr bool operator==(const month_weekday& x, const month_weekday& y) noexcept;
+constexpr bool operator!=(const month_weekday& x, const month_weekday& y) noexcept;
+
+// 25.8.12, class month_weekday_last    // C++20
+class month_weekday_last;
+
+constexpr bool operator==(const month_weekday_last& x, const month_weekday_last& y) noexcept;
+constexpr bool operator!=(const month_weekday_last& x, const month_weekday_last& y) noexcept;
+
+
+// 25.8.13, class year_month    // C++20
+class year_month;
+
+constexpr bool operator==(const year_month& x, const year_month& y) noexcept;
+constexpr bool operator!=(const year_month& x, const year_month& y) noexcept;
+constexpr bool operator< (const year_month& x, const year_month& y) noexcept;
+constexpr bool operator> (const year_month& x, const year_month& y) noexcept;
+constexpr bool operator<=(const year_month& x, const year_month& y) noexcept;
+constexpr bool operator>=(const year_month& x, const year_month& y) noexcept;
+
+constexpr year_month operator+(const year_month& ym, const months& dm) noexcept;
+constexpr year_month operator+(const months& dm, const year_month& ym) noexcept;
+constexpr year_month operator-(const year_month& ym, const months& dm) noexcept;
+constexpr months operator-(const year_month& x, const year_month& y) noexcept;
+constexpr year_month operator+(const year_month& ym, const years& dy) noexcept;
+constexpr year_month operator+(const years& dy, const year_month& ym) noexcept;
+constexpr year_month operator-(const year_month& ym, const years& dy) noexcept;
+
+// 25.8.14, class year_month_day class    // C++20
+year_month_day;
+
+constexpr bool operator==(const year_month_day& x, const year_month_day& y) noexcept;
+constexpr bool operator!=(const year_month_day& x, const year_month_day& y) noexcept;
+constexpr bool operator< (const year_month_day& x, const year_month_day& y) noexcept;
+constexpr bool operator> (const year_month_day& x, const year_month_day& y) noexcept;
+constexpr bool operator<=(const year_month_day& x, const year_month_day& y) noexcept;
+constexpr bool operator>=(const year_month_day& x, const year_month_day& y) noexcept;
+
+constexpr year_month_day operator+(const year_month_day& ymd, const months& dm) noexcept;
+constexpr year_month_day operator+(const months& dm, const year_month_day& ymd) noexcept;
+constexpr year_month_day operator+(const year_month_day& ymd, const years& dy) noexcept;
+constexpr year_month_day operator+(const years& dy, const year_month_day& ymd) noexcept;
+constexpr year_month_day operator-(const year_month_day& ymd, const months& dm) noexcept;
+constexpr year_month_day operator-(const year_month_day& ymd, const years& dy) noexcept;
+
+
+// 25.8.15, class year_month_day_last    // C++20
+class year_month_day_last;
+
+constexpr bool operator==(const year_month_day_last& x,
+                          const year_month_day_last& y) noexcept;
+constexpr bool operator!=(const year_month_day_last& x,
+                          const year_month_day_last& y) noexcept;
+constexpr bool operator< (const year_month_day_last& x,
+                          const year_month_day_last& y) noexcept;
+constexpr bool operator> (const year_month_day_last& x,
+                          const year_month_day_last& y) noexcept;
+constexpr bool operator<=(const year_month_day_last& x,
+                          const year_month_day_last& y) noexcept;
+constexpr bool operator>=(const year_month_day_last& x,
+                          const year_month_day_last& y) noexcept;
+
+constexpr year_month_day_last
+  operator+(const year_month_day_last& ymdl, const months& dm) noexcept;
+constexpr year_month_day_last
+  operator+(const months& dm, const year_month_day_last& ymdl) noexcept;
+constexpr year_month_day_last
+  operator+(const year_month_day_last& ymdl, const years& dy) noexcept;
+constexpr year_month_day_last
+  operator+(const years& dy, const year_month_day_last& ymdl) noexcept;
+constexpr year_month_day_last
+  operator-(const year_month_day_last& ymdl, const months& dm) noexcept;
+constexpr year_month_day_last
+  operator-(const year_month_day_last& ymdl, const years& dy) noexcept;
+
+// 25.8.16, class year_month_weekday    // C++20
+class year_month_weekday;
+
+constexpr bool operator==(const year_month_weekday& x,
+                          const year_month_weekday& y) noexcept;
+constexpr bool operator!=(const year_month_weekday& x,
+                          const year_month_weekday& y) noexcept;
+
+constexpr year_month_weekday
+  operator+(const year_month_weekday& ymwd, const months& dm) noexcept;
+constexpr year_month_weekday
+  operator+(const months& dm, const year_month_weekday& ymwd) noexcept;
+constexpr year_month_weekday
+  operator+(const year_month_weekday& ymwd, const years& dy) noexcept;
+constexpr year_month_weekday
+  operator+(const years& dy, const year_month_weekday& ymwd) noexcept;
+constexpr year_month_weekday
+  operator-(const year_month_weekday& ymwd, const months& dm) noexcept;
+constexpr year_month_weekday
+  operator-(const year_month_weekday& ymwd, const years& dy) noexcept;
+
+// 25.8.17, class year_month_weekday_last    // C++20
+class year_month_weekday_last;
+
+constexpr bool operator==(const year_month_weekday_last& x,
+                          const year_month_weekday_last& y) noexcept;
+constexpr bool operator!=(const year_month_weekday_last& x,
+                          const year_month_weekday_last& y) noexcept;
+constexpr year_month_weekday_last
+  operator+(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
+constexpr year_month_weekday_last
+  operator+(const months& dm, const year_month_weekday_last& ymwdl) noexcept;
+constexpr year_month_weekday_last
+  operator+(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
+constexpr year_month_weekday_last
+  operator+(const years& dy, const year_month_weekday_last& ymwdl) noexcept;
+constexpr year_month_weekday_last
+  operator-(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
+constexpr year_month_weekday_last
+  operator-(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
+  
+// 25.8.18, civil calendar conventional syntax operators    // C++20
+constexpr year_month
+  operator/(const year& y, const month& m) noexcept;
+constexpr year_month
+  operator/(const year& y, int m) noexcept;
+constexpr month_day
+  operator/(const month& m, const day& d) noexcept;
+constexpr month_day
+  operator/(const month& m, int d) noexcept;
+constexpr month_day
+  operator/(int m, const day& d) noexcept;
+constexpr month_day
+  operator/(const day& d, const month& m) noexcept;
+constexpr month_day
+  operator/(const day& d, int m) noexcept;
+constexpr month_day_last
+  operator/(const month& m, last_spec) noexcept;
+constexpr month_day_last
+  operator/(int m, last_spec) noexcept;
+constexpr month_day_last
+  operator/(last_spec, const month& m) noexcept;
+constexpr month_day_last
+  operator/(last_spec, int m) noexcept;
+constexpr month_weekday
+  operator/(const month& m, const weekday_indexed& wdi) noexcept;
+constexpr month_weekday
+  operator/(int m, const weekday_indexed& wdi) noexcept;
+constexpr month_weekday
+  operator/(const weekday_indexed& wdi, const month& m) noexcept;
+constexpr month_weekday
+  operator/(const weekday_indexed& wdi, int m) noexcept;
+constexpr month_weekday_last
+  operator/(const month& m, const weekday_last& wdl) noexcept;
+constexpr month_weekday_last
+  operator/(int m, const weekday_last& wdl) noexcept;
+constexpr month_weekday_last
+  operator/(const weekday_last& wdl, const month& m) noexcept;
+constexpr month_weekday_last
+  operator/(const weekday_last& wdl, int m) noexcept;
+constexpr year_month_day
+  operator/(const year_month& ym, const day& d) noexcept;
+constexpr year_month_day
+  operator/(const year_month& ym, int d) noexcept;
+constexpr year_month_day
+  operator/(const year& y, const month_day& md) noexcept;
+constexpr year_month_day
+  operator/(int y, const month_day& md) noexcept;
+constexpr year_month_day
+  operator/(const month_day& md, const year& y) noexcept;
+constexpr year_month_day
+  operator/(const month_day& md, int y) noexcept;
+constexpr year_month_day_last
+  operator/(const year_month& ym, last_spec) noexcept;
+constexpr year_month_day_last
+  operator/(const year& y, const month_day_last& mdl) noexcept;
+constexpr year_month_day_last
+  operator/(int y, const month_day_last& mdl) noexcept;
+constexpr year_month_day_last
+  operator/(const month_day_last& mdl, const year& y) noexcept;
+constexpr year_month_day_last
+  operator/(const month_day_last& mdl, int y) noexcept;
+constexpr year_month_weekday
+  operator/(const year_month& ym, const weekday_indexed& wdi) noexcept;
+constexpr year_month_weekday
+  operator/(const year& y, const month_weekday& mwd) noexcept;
+constexpr year_month_weekday
+  operator/(int y, const month_weekday& mwd) noexcept;
+constexpr year_month_weekday
+  operator/(const month_weekday& mwd, const year& y) noexcept;
+constexpr year_month_weekday
+  operator/(const month_weekday& mwd, int y) noexcept;
+constexpr year_month_weekday_last
+  operator/(const year_month& ym, const weekday_last& wdl) noexcept;
+constexpr year_month_weekday_last
+  operator/(const year& y, const month_weekday_last& mwdl) noexcept;
+constexpr year_month_weekday_last
+  operator/(int y, const month_weekday_last& mwdl) noexcept;
+constexpr year_month_weekday_last
+  operator/(const month_weekday_last& mwdl, const year& y) noexcept;
+constexpr year_month_weekday_last
+  operator/(const month_weekday_last& mwdl, int y) noexcept;  
+
+// 25.9, class template time_of_day    // C++20
+template<class Duration> class time_of_day;
+
+template<> class time_of_day<hours>;
+template<> class time_of_day<minutes>;
+template<> class time_of_day<seconds>;
+template<class Rep, class Period> class time_of_day<duration<Rep, Period>>;
+
+// 25.10.2, time zone database     // C++20
+struct tzdb;
+class tzdb_list;
+
+// 25.10.2.3, time zone database access    // C++20
+const tzdb& get_tzdb();
+tzdb_list& get_tzdb_list();
+const time_zone* locate_zone(string_view tz_name);
+const time_zone* current_zone();
+
+// 25.10.2.4, remote time zone database support    // C++20
+const tzdb& reload_tzdb();
+string remote_version();
+
+// 25.10.3, exception classes    // C++20
+class nonexistent_local_time;
+class ambiguous_local_time;
+
+// 25.10.4, information classes    // C++20
+struct sys_info;
+struct local_info;
+    
+// 25.10.5, class time_zone    // C++20
+enum class choose {earliest, latest};
+class time_zone;
+bool operator==(const time_zone& x, const time_zone& y) noexcept;
+bool operator!=(const time_zone& x, const time_zone& y) noexcept;
+bool operator<(const time_zone& x, const time_zone& y) noexcept;
+bool operator>(const time_zone& x, const time_zone& y) noexcept;
+bool operator<=(const time_zone& x, const time_zone& y) noexcept;
+bool operator>=(const time_zone& x, const time_zone& y) noexcept;
+  
+// 25.10.6, class template zoned_traits    // C++20
+template<class T> struct zoned_traits;
+
+// 25.10.7, class template zoned_time    // C++20
+template<class Duration, class TimeZonePtr = const time_zone*> class zoned_time;
+using zoned_seconds = zoned_time<seconds>;
+
+template<class Duration1, class Duration2, class TimeZonePtr>
+  bool operator==(const zoned_time<Duration1, TimeZonePtr>& x,
+                  const zoned_time<Duration2, TimeZonePtr>& y);
+template<class Duration1, class Duration2, class TimeZonePtr>
+  bool operator!=(const zoned_time<Duration1, TimeZonePtr>& x,
+                  const zoned_time<Duration2, TimeZonePtr>& y);
+
+// 25.10.8, leap second support    // C++20
+class leap;
+
+bool operator==(const leap& x, const leap& y);
+bool operator!=(const leap& x, const leap& y);
+bool operator< (const leap& x, const leap& y);
+bool operator> (const leap& x, const leap& y);
+bool operator<=(const leap& x, const leap& y);
+bool operator>=(const leap& x, const leap& y);
+template<class Duration>
+  bool operator==(const leap& x, const sys_time<Duration>& y);
+template<class Duration>
+  bool operator==(const sys_time<Duration>& x, const leap& y);
+template<class Duration>
+  bool operator!=(const leap& x, const sys_time<Duration>& y);
+template<class Duration>
+  bool operator!=(const sys_time<Duration>& x, const leap& y);
+template<class Duration>
+  bool operator< (const leap& x, const sys_time<Duration>& y);
+template<class Duration>
+  bool operator< (const sys_time<Duration>& x, const leap& y);
+template<class Duration>
+  bool operator> (const leap& x, const sys_time<Duration>& y);
+template<class Duration>
+  bool operator> (const sys_time<Duration>& x, const leap& y);
+template<class Duration>
+  bool operator<=(const leap& x, const sys_time<Duration>& y);
+template<class Duration>
+  bool operator<=(const sys_time<Duration>& x, const leap& y);
+template<class Duration>
+  bool operator>=(const leap& x, const sys_time<Duration>& y);
+template<class Duration>
+  bool operator>=(const sys_time<Duration>& x, const leap& y);
+
+// 25.10.9, class link    // C++20
+class link;
+bool operator==(const link& x, const link& y);
+bool operator!=(const link& x, const link& y);
+bool operator< (const link& x, const link& y);
+bool operator> (const link& x, const link& y);
+bool operator<=(const link& x, const link& y);
+bool operator>=(const link& x, const link& y);
+
+// 25.11, formatting    // C++20
+template<class charT, class Streamable>
+  basic_string<charT>
+    format(const charT* fmt, const Streamable& s);
+
+template<class charT, class Streamable>
+  basic_string<charT>
+    format(const locale& loc, const charT* fmt, const Streamable& s);
+
+template<class charT, class traits, class Alloc, class Streamable>
+  basic_string<charT, traits, Alloc>
+    format(const basic_string<charT, traits, Alloc>& fmt, const Streamable& s);
+
+template<class charT, class traits, class Alloc, class Streamable>
+  basic_string<charT, traits, Alloc>
+    format(const locale& loc, const basic_string<charT, traits, Alloc>& fmt,
+           const Streamable& s);             
+
+// 25.12, parsing    // C++20
+template<class charT, class traits, class Alloc, class Parsable>
+unspecified
+    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp);
+
+template<class charT, class traits, class Alloc, class Parsable>
+unspecified
+    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp,
+          basic_string<charT, traits, Alloc>& abbrev);
+
+template<class charT, class traits, class Alloc, class Parsable>
+unspecified
+    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp,
+          minutes& offset);
+
+template<class charT, class traits, class Alloc, class Parsable>
+unspecified
+    parse(const basic_string<charT, traits, Alloc>& format, Parsable& tp,
+          basic_string<charT, traits, Alloc>& abbrev, minutes& offset);
+
+inline constexpr last_spec								last{};       // C++20
+inline constexpr chrono::weekday                        Sunday{0};    // C++20
+inline constexpr chrono::weekday                        Monday{1};    // C++20
+inline constexpr chrono::weekday                        Tuesday{2};   // C++20
+inline constexpr chrono::weekday                        Wednesday{3}; // C++20
+inline constexpr chrono::weekday                        Thursday{4};  // C++20
+inline constexpr chrono::weekday                        Friday{5};    // C++20
+inline constexpr chrono::weekday                        Saturday{6};  // C++20
+
+inline constexpr chrono::month                          January{1};   // C++20
+inline constexpr chrono::month                          February{2};  // C++20
+inline constexpr chrono::month                          March{3};     // C++20
+inline constexpr chrono::month                          April{4};     // C++20
+inline constexpr chrono::month                          May{5};       // C++20
+inline constexpr chrono::month                          June{6};      // C++20
+inline constexpr chrono::month                          July{7};      // C++20
+inline constexpr chrono::month                          August{8};    // C++20
+inline constexpr chrono::month                          September{9}; // C++20
+inline constexpr chrono::month                          October{10};  // C++20
+inline constexpr chrono::month                          November{11}; // C++20
+inline constexpr chrono::month                          December{12}; // C++20
 }  // chrono
 
+inline namespace literals {
+  inline namespace chrono_literals {
 constexpr chrono::hours                                 operator ""h(unsigned long long); // C++14
 constexpr chrono::duration<unspecified , ratio<3600,1>> operator ""h(long double); // C++14
 constexpr chrono::minutes                               operator ""min(unsigned long long); // C++14
@@ -295,6 +783,10 @@ constexpr chrono::microseconds                          operator ""us(unsigned l
 constexpr chrono::duration<unspecified , micro>         operator ""us(long double); // C++14
 constexpr chrono::nanoseconds                           operator ""ns(unsigned long long); // C++14
 constexpr chrono::duration<unspecified , nano>          operator ""ns(long double); // C++14
+constexpr chrono::day                                   operator ""d(unsigned long long d) noexcept; // C++20
+constexpr chrono::year                                  operator ""y(unsigned long long y) noexcept; // C++20
+}  // chrono_literals
+}  // literals
 
 }  // std
 */