27 Time library [time]

27.7 Clocks [time.clock]

27.7.1 Class system_­clock [time.clock.system]

27.7.1.2 Members [time.clock.system.members]

using system_clock::rep = unspecified;
Requires: system_­clock​::​duration​::​min() < system_­clock​::​duration​::​zero() shall be true.

Note
:
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.