29 Time library [time]

29.6 Class template time_­point [time.point]

29.6.2 Constructors [time.point.cons]

constexpr time_point();
Effects: Initializes d_­ with duration​::​zero().
Such a time_­point object represents the epoch.
constexpr explicit time_point(const duration& d);
Effects: Initializes d_­ with d.
Such a time_­point object represents the epoch + d.
template<class Duration2> constexpr time_point(const time_point<clock, Duration2>& t);
Constraints: is_­convertible_­v<Duration2, duration> is true.
Effects: Initializes d_­ with t.time_­since_­epoch().