29 Time library [time]

29.11 Time zones [time.zone]

29.11.8 Class leap_second [time.zone.leap]

29.11.8.1 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; }; }
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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.
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[Example 1: for (auto& l : get_tzdb().leap_seconds) if (l <= sys_days{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]

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

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constexpr sys_seconds date() const noexcept;
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Returns: The date and time at which the leap second was inserted.
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constexpr seconds value() const noexcept;
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Returns: +1s to indicate a positive leap second or -1s to indicate a negative leap second.
[Note 1: 
All leap seconds inserted up through 2022 were positive leap seconds.
— end note]

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

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