27 Time library [time]

27.11 Time zones [time.zone]

27.11.8 Class leap_­second [time.zone.leap]

27.11.8.1 Overview [time.zone.leap.overview]

namespace std::chrono {
  class leap_second {
  public:
    leap_second(const leap_second&)            = default;
    leap_second& operator=(const leap_second&) = default;

    // unspecified additional constructors

    constexpr sys_seconds date() const noexcept;
    constexpr seconds value() const noexcept;
  };
}
Objects of type leap_­second representing the date and value of the leap second insertions are constructed and stored in the time zone database when initialized.
[Example:
for (auto& l : get_tzdb().leap_seconds)
  if (l <= 2018y/March/17d)
    cout << l.date() << ": " << l.value() << '\n';
Produces the output:
1972-07-01 00:00:00: 1s
1973-01-01 00:00:00: 1s
1974-01-01 00:00:00: 1s
1975-01-01 00:00:00: 1s
1976-01-01 00:00:00: 1s
1977-01-01 00:00:00: 1s
1978-01-01 00:00:00: 1s
1979-01-01 00:00:00: 1s
1980-01-01 00:00:00: 1s
1981-07-01 00:00:00: 1s
1982-07-01 00:00:00: 1s
1983-07-01 00:00:00: 1s
1985-07-01 00:00:00: 1s
1988-01-01 00:00:00: 1s
1990-01-01 00:00:00: 1s
1991-01-01 00:00:00: 1s
1992-07-01 00:00:00: 1s
1993-07-01 00:00:00: 1s
1994-07-01 00:00:00: 1s
1996-01-01 00:00:00: 1s
1997-07-01 00:00:00: 1s
1999-01-01 00:00:00: 1s
2006-01-01 00:00:00: 1s
2009-01-01 00:00:00: 1s
2012-07-01 00:00:00: 1s
2015-07-01 00:00:00: 1s
2017-01-01 00:00:00: 1s
— end example]

27.11.8.2 Member functions [time.zone.leap.members]

constexpr sys_seconds date() const noexcept;
Returns: The date and time at which the leap second was inserted.
constexpr seconds value() const noexcept;
Returns: +1s to indicate a positive leap second or -1s to indicate a negative leap second.
[Note:
All leap seconds inserted up through 2019 were positive leap seconds.
— end note]

27.11.8.3 Non-member functions [time.zone.leap.nonmembers]

constexpr bool operator==(const leap_second& x, const leap_second& y) noexcept;
Returns: x.date() == y.date().
constexpr strong_ordering operator<=>(const leap_second& x, const leap_second& y) noexcept;
Returns: x.date() <=> y.date().
template<class Duration> constexpr bool operator==(const leap_second& x, const sys_time<Duration>& y) noexcept;
Returns: x.date() == y.
template<class Duration> constexpr bool operator<(const leap_second& x, const sys_time<Duration>& y) noexcept;
Returns: x.date() < y.
template<class Duration> constexpr bool operator<(const sys_time<Duration>& x, const leap_second& y) noexcept;
Returns: x < y.date().
template<class Duration> constexpr bool operator>(const leap_second& x, const sys_time<Duration>& y) noexcept;
Returns: y < x.
template<class Duration> constexpr bool operator>(const sys_time<Duration>& x, const leap_second& y) noexcept;
Returns: y < x.
template<class Duration> constexpr bool operator<=(const leap_second& x, const sys_time<Duration>& y) noexcept;
Returns: !(y < x).
template<class Duration> constexpr bool operator<=(const sys_time<Duration>& x, const leap_second& y) noexcept;
Returns: !(y < x).
template<class Duration> constexpr bool operator>=(const leap_second& x, const sys_time<Duration>& y) noexcept;
Returns: !(x < y).
template<class Duration> constexpr bool operator>=(const sys_time<Duration>& x, const leap_second& y) noexcept;
Returns: !(x < y).
template<class Duration> requires three_­way_­comparable_­with<sys_seconds, sys_time<Duration>> constexpr auto operator<=>(const leap_second& x, const sys_time<Duration>& y) noexcept;
Returns: x.date() <=> y.