27 Time library [time]

27.6 Class template time_­point [time.point]

27.6.1 General [time.point.general]

namespace std::chrono { 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++(); constexpr time_point operator++(int); constexpr time_point& operator--(); constexpr time_point operator--(int); constexpr time_point& operator+=(const duration& d); constexpr time_point& operator-=(const duration& d); // [time.point.special], special values static constexpr time_point min() noexcept; static constexpr time_point max() noexcept; }; }
If Duration is not a specialization of duration, the program is ill-formed.

27.6.2 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().

27.6.3 Observer [time.point.observer]

constexpr duration time_since_epoch() const;
Returns: d_­.

27.6.4 Arithmetic [time.point.arithmetic]

constexpr time_point& operator++();
Effects: Equivalent to: ++d_­.
Returns: *this.
constexpr time_point operator++(int);
Effects: Equivalent to: return time_­point{d_­++};
constexpr time_point& operator--();
Effects: Equivalent to: --d_­.
Returns: *this.
constexpr time_point operator--(int);
Effects: Equivalent to: return time_­point{d_­--};
constexpr time_point& operator+=(const duration& d);
Effects: Equivalent to: d_­ += d.
Returns: *this.
constexpr time_point& operator-=(const duration& d);
Effects: Equivalent to: d_­ -= d.
Returns: *this.

27.6.5 Special values [time.point.special]

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

27.6.6 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().

27.6.7 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.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).
template<class Clock, class Duration1, three_­way_­comparable_­with<Duration1> Duration2> constexpr auto operator<=>(const time_point<Clock, Duration1>& lhs, const time_point<Clock, Duration2>& rhs);
Returns: lhs.time_­since_­epoch() <=> rhs.time_­since_­epoch().

27.6.8 Conversions [time.point.cast]

template<class ToDuration, class Clock, class Duration> constexpr time_point<Clock, ToDuration> time_point_cast(const time_point<Clock, Duration>& t);
Constraints: 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);
Constraints: 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);
Constraints: 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);
Constraints: 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())).