23 General utilities library [utilities]

23.17 Time utilities [time]

23.17.6 Class template time_­point [time.point]

template <class Clock, class Duration = typename Clock::duration>
class time_point {
public:
  using clock    = Clock;
  using duration = Duration;
  using rep      = typename duration::rep;
  using period   = typename duration::period;
private:
  duration d_;  // exposition only

public:
  // [time.point.cons], construct
  constexpr time_point();  // has value epoch
  constexpr explicit time_point(const duration& d);  // same as time_­point() + d
  template <class Duration2>
    constexpr time_point(const time_point<clock, Duration2>& t);

  // [time.point.observer], observer
  constexpr duration time_since_epoch() const;

  // [time.point.arithmetic], arithmetic
  constexpr time_point& operator+=(const duration& d);
  constexpr time_point& operator-=(const duration& d);

  // [time.point.special], special values
  static constexpr time_point min();
  static constexpr time_point max();
};
Clock shall meet the Clock requirements.
If Duration is not an instance of duration, the program is ill-formed.

23.17.6.1 time_­point constructors [time.point.cons]

constexpr time_point();
Effects: Constructs an object of type time_­point, initializing d_­ with duration​::​zero().
Such a time_­point object represents the epoch.
constexpr explicit time_point(const duration& d);
Effects: Constructs an object of type time_­point, initializing d_­ with d.
Such a time_­point object represents the epoch + d.
template <class Duration2> constexpr time_point(const time_point<clock, Duration2>& t);
Remarks: This constructor shall not participate in overload resolution unless Duration2 is implicitly convertible to duration.
Effects: Constructs an object of type time_­point, initializing d_­ with t.time_­since_­epoch().

23.17.6.2 time_­point observer [time.point.observer]

constexpr duration time_since_epoch() const;
Returns: d_­.

23.17.6.3 time_­point arithmetic [time.point.arithmetic]

constexpr time_point& operator+=(const duration& d);
Effects: As if by: d_­ += d;
Returns: *this.
constexpr time_point& operator-=(const duration& d);
Effects: As if by: d_­ -= d;
Returns: *this.

23.17.6.4 time_­point special values [time.point.special]

static constexpr time_point min();
Returns: time_­point(duration​::​min()).
static constexpr time_point max();
Returns: time_­point(duration​::​max()).

23.17.6.5 time_­point non-member arithmetic [time.point.nonmember]

template <class Clock, class Duration1, class Rep2, class Period2> constexpr time_point<Clock, common_type_t<Duration1, duration<Rep2, Period2>>> operator+(const time_point<Clock, Duration1>& lhs, const duration<Rep2, Period2>& rhs);
Returns: CT(lhs.time_­since_­epoch() + rhs), where CT is the type of the return value.
template <class Rep1, class Period1, class Clock, class Duration2> constexpr time_point<Clock, common_type_t<duration<Rep1, Period1>, Duration2>> operator+(const duration<Rep1, Period1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: rhs + lhs.
template <class Clock, class Duration1, class Rep2, class Period2> constexpr time_point<Clock, common_type_t<Duration1, duration<Rep2, Period2>>> operator-(const time_point<Clock, Duration1>& lhs, const duration<Rep2, Period2>& rhs);
Returns: CT(lhs.time_­since_­epoch() - rhs), where CT is the type of the return value.
template <class Clock, class Duration1, class Duration2> constexpr common_type_t<Duration1, Duration2> operator-(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: lhs.time_­since_­epoch() - rhs.time_­since_­epoch().

23.17.6.6 time_­point comparisons [time.point.comparisons]

template <class Clock, class Duration1, class Duration2> constexpr bool operator==(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: lhs.time_­since_­epoch() == rhs.time_­since_­epoch().
template <class Clock, class Duration1, class Duration2> constexpr bool operator!=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: !(lhs == rhs).
template <class Clock, class Duration1, class Duration2> constexpr bool operator<(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: lhs.time_­since_­epoch() < rhs.time_­since_­epoch().
template <class Clock, class Duration1, class Duration2> constexpr bool operator<=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: !(rhs < lhs).
template <class Clock, class Duration1, class Duration2> constexpr bool operator>(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: rhs < lhs.
template <class Clock, class Duration1, class Duration2> constexpr bool operator>=(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: !(lhs < rhs).

23.17.6.7 time_­point_­cast [time.point.cast]

template <class ToDuration, class Clock, class Duration> constexpr time_point<Clock, ToDuration> time_point_cast(const time_point<Clock, Duration>& t);
Remarks: This function shall not participate in overload resolution unless ToDuration is a specialization of duration.
Returns:
time_point<Clock, ToDuration>(duration_cast<ToDuration>(t.time_since_epoch()))
template <class ToDuration, class Clock, class Duration> constexpr time_point<Clock, ToDuration> floor(const time_point<Clock, Duration>& tp);
Remarks: This function shall not participate in overload resolution unless ToDuration is a specialization of duration.
Returns: time_­point<Clock, ToDuration>(floor<ToDuration>(tp.time_­since_­epoch())).
template <class ToDuration, class Clock, class Duration> constexpr time_point<Clock, ToDuration> ceil(const time_point<Clock, Duration>& tp);
Remarks: This function shall not participate in overload resolution unless ToDuration is a specialization of duration.
Returns: time_­point<Clock, ToDuration>(ceil<ToDuration>(tp.time_­since_­epoch())).
template <class ToDuration, class Clock, class Duration> constexpr time_point<Clock, ToDuration> round(const time_point<Clock, Duration>& tp);
Remarks: This function shall not participate in overload resolution unless ToDuration is a specialization of duration, and treat_­as_­floating_­point_­v<typename ToDuration​::​rep> is false.
Returns: time_­point<Clock, ToDuration>(round<ToDuration>(tp.time_­since_­epoch())).