29 Time library [time]

29.7 Clocks [time.clock]

29.7.2 Class system_clock [time.clock.system]

29.7.2.2 Members [time.clock.system.members]

using system_clock::rep = unspecified;
Constraints: system_clock​::​duration​::​min() < system_clock​::​duration​::​zero() is true.
[Note 1: 
This implies that rep is a signed type.
— end note]
static time_t to_time_t(const time_point& t) noexcept;
Returns: A time_t object that represents the same point in time as t when both values are restricted to the coarser of the precisions of time_t and time_point.
It is implementation-defined whether values are rounded or truncated to the required precision.
static time_point from_time_t(time_t t) noexcept;
Returns: A time_point object that represents the same point in time as t when both values are restricted to the coarser of the precisions of time_t and time_point.
It is implementation-defined whether values are rounded or truncated to the required precision.