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 International 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 second 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 TrivialClock
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::formatter that formats
(C++20) a tai_time according to the provided format
(class template specialization)

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 representing 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 adjustment, 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)