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std::chrono::tai_clock(3)     C++ Standard Libary    std::chrono::tai_clock(3)

NAME
       std::chrono::tai_clock -	std::chrono::tai_clock

Synopsis
	  Defined in header <chrono>
	  class	tai_clock;	      (since C++20)

	  The clock std::chrono::tai_clock is a	Clock that represents Interna-
       tional Atomic
	  Time	(TAI). It measures time	since 00:00:00,	1 January 1958,	and is
       offset 10
	  seconds ahead	of UTC at  that	 date  (i.e.,  its  epoch,  1958-01-01
       00:00:00	TAI, is
	  1957-12-31 23:59:50 UTC).

	  Leap seconds are not inserted	into TAI. Thus,	every time a leap sec-
       ond is inserted
	  into	UTC, UTC falls another second behind TAI. As of	December 2017,
       UTC is 37
	  seconds behind TAI, reflecting the 10-second initial offset and  the
       27 leap seconds
	  inserted  between  1958  and	2017. Thus, 2018-01-01 00:00:00	UTC is
       equivalent to
	  2018-01-01 00:00:37 TAI.

	  tai_clock meets the Clock requirements. It does not meet  the	 Triv-
       ialClock
	  requirements unless the implementation can guarantee that now() does
       not throw an
	  exception.

	 Time point family

	  Defined in namespace std::chrono
	  template<class Duration>
	  using	  tai_time  =  std::chrono::time_point<std::chrono::tai_clock,
       (since C++20)
	  Duration>;
	  using	     tai_seconds       =       tai_time<std::chrono::seconds>;
       (since C++20)

	  operator<<(std::chrono::tai_time)	 performs  stream  output on a
       tai_time
	  (C++20)				(function template)
	  from_stream(std::chrono::tai_time)	 parses	 a  tai_time  from   a
       stream according	to
	  (C++20)				the provided format
						(function template)
	  std::formatter<std::chrono::tai_time>	specialization of std::format-
       ter that	formats
	  (C++20)				 a  tai_time  according	to the
       provided	format
						(class	template   specializa-
       tion)

Member types
	  Member type Definition
	  rep	       signed arithmetic type representing the number of ticks
       in the clock's
		      duration
	  period      a	std::ratio type	representing the tick  period  of  the
       clock, in seconds
	  duration     std::chrono::duration<rep,  period>,  capable of	repre-
       senting negative
		      durations
	  time_point  std::chrono::time_point<std::chrono::tai_clock>

Member constants
				   true	if the time between  ticks  is	always
       constant, i.e.
	  constexpr  bool is_steady calls to now() return values that increase
       monotonically
	  [static]		   even	in case	of some	external clock adjust-
       ment, otherwise
				   false
				   (public static member constant)

Member functions
	  now	   returns a std::chrono::time_point representing the  current
       point in	time
	  [static] (public static member function)
	  to_utc   converts tai_time to	utc_time
	  [static] (public static member function)
	  from_utc converts utc_time to	tai_time
	  [static] (public static member function)

http://cppreference.com		  2022.07.31	     std::chrono::tai_clock(3)

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