27 Time library [time]

27.11 Time zones [time.zone]

27.11.7 Class template zoned_­time [time.zone.zonedtime]

27.11.7.1 Overview [time.zone.zonedtime.overview]

namespace std::chrono { template<class Duration, class TimeZonePtr = const time_zone*> class zoned_time { public: using duration = common_type_t<Duration, seconds>; private: TimeZonePtr zone_; // exposition only sys_time<duration> tp_; // exposition only using traits = zoned_traits<TimeZonePtr>; // exposition only public: zoned_time(); zoned_time(const zoned_time&) = default; zoned_time& operator=(const zoned_time&) = default; zoned_time(const sys_time<Duration>& st); explicit zoned_time(TimeZonePtr z); explicit zoned_time(string_view name); template<class Duration2> zoned_time(const zoned_time<Duration2, TimeZonePtr>& zt); zoned_time(TimeZonePtr z, const sys_time<Duration>& st); zoned_time(string_view name, const sys_time<Duration>& st); zoned_time(TimeZonePtr z, const local_time<Duration>& tp); zoned_time(string_view name, const local_time<Duration>& tp); zoned_time(TimeZonePtr z, const local_time<Duration>& tp, choose c); zoned_time(string_view name, const local_time<Duration>& tp, choose c); template<class Duration2, class TimeZonePtr2> zoned_time(TimeZonePtr z, const zoned_time<Duration2, TimeZonePtr2>& zt); template<class Duration2, class TimeZonePtr2> zoned_time(TimeZonePtr z, const zoned_time<Duration2, TimeZonePtr2>& zt, choose); template<class Duration2, class TimeZonePtr2> zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& zt); template<class Duration2, class TimeZonePtr2> zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& zt, choose); zoned_time& operator=(const sys_time<Duration>& st); zoned_time& operator=(const local_time<Duration>& ut); operator sys_time<duration>() const; explicit operator local_time<duration>() const; TimeZonePtr get_time_zone() const; local_time<duration> get_local_time() const; sys_time<duration> get_sys_time() const; sys_info get_info() const; }; zoned_time() -> zoned_time<seconds>; template<class Duration> zoned_time(sys_time<Duration>) -> zoned_time<common_type_t<Duration, seconds>>; template<class TimeZonePtrOrName> using time-zone-representation = // exposition only conditional_t<is_convertible_v<TimeZonePtrOrName, string_view>, const time_zone*, remove_cvref_t<TimeZonePtrOrName>>; template<class TimeZonePtrOrName> zoned_time(TimeZonePtrOrName&&) -> zoned_time<seconds, time-zone-representation<TimeZonePtrOrName>>; template<class TimeZonePtrOrName, class Duration> zoned_time(TimeZonePtrOrName&&, sys_time<Duration>) -> zoned_time<common_type_t<Duration, seconds>, time-zone-representation<TimeZonePtrOrName>>; template<class TimeZonePtrOrName, class Duration> zoned_time(TimeZonePtrOrName&&, local_time<Duration>, choose = choose::earliest) -> zoned_time<common_type_t<Duration, seconds>, time-zone-representation<TimeZonePtrOrName>>; template<class Duration, class TimeZonePtrOrName, class TimeZonePtr2> zoned_time(TimeZonePtrOrName&&, zoned_time<Duration, TimeZonePtr2>, choose = choose::earliest) -> zoned_time<common_type_t<Duration, seconds>, time-zone-representation<TimeZonePtrOrName>>; }
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zoned_­time represents a logical pairing of a time_­zone and a time_­point with precision Duration.
zoned_­time<Duration> maintains the invariant that it always refers to a valid time zone and represents a point in time that exists and is not ambiguous in that time zone.
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If Duration is not a specialization of chrono​::​duration, the program is ill-formed.
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Every constructor of zoned_­time that accepts a string_­view as its first parameter does not participate in class template argument deduction ([over.match.class.deduct]).

27.11.7.2 Constructors [time.zone.zonedtime.ctor]

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zoned_time();
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Constraints: traits​::​default_­zone() is a well-formed expression.
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Effects: Initializes zone_­ with traits​::​default_­zone() and default constructs tp_­.
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zoned_time(const sys_time<Duration>& st);
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Constraints: traits​::​default_­zone() is a well-formed expression.
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Effects: Initializes zone_­ with traits​::​default_­zone() and tp_­ with st.
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explicit zoned_time(TimeZonePtr z);
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Preconditions: z refers to a time zone.
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Effects: Initializes zone_­ with std​::​move(z) and default constructs tp_­.
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explicit zoned_time(string_view name);
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Constraints: traits​::​locate_­zone(string_­view{}) is a well-formed expression and zoned_­time is constructible from the return type of traits​::​locate_­zone(string_­view{}).
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Effects: Initializes zone_­ with traits​::​locate_­zone(name) and default constructs tp_­.
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template<class Duration2> zoned_time(const zoned_time<Duration2, TimeZonePtr>& y);
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Constraints: is_­convertible_­v<sys_­time<Duration2>, sys_­time<Duration>> is true.
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Effects: Initializes zone_­ with y.zone_­ and tp_­ with y.tp_­.
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zoned_time(TimeZonePtr z, const sys_time<Duration>& st);
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Preconditions: z refers to a time zone.
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Effects: Initializes zone_­ with std​::​move(z) and tp_­ with st.
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zoned_time(string_view name, const sys_time<Duration>& st);
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Constraints: zoned_­time is constructible from the return type of traits​::​locate_­zone(name) and st.
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Effects: Equivalent to construction with {traits​::​locate_­zone(name), st}.
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zoned_time(TimeZonePtr z, const local_time<Duration>& tp);
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Constraints: is_convertible_v< decltype(declval<TimeZonePtr&>()->to_sys(local_time<Duration>{})), sys_time<duration>> is true.
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Preconditions: z refers to a time zone.
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Effects: Initializes zone_­ with std​::​move(z) and tp_­ with zone_­->to_­sys(tp).
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zoned_time(string_view name, const local_time<Duration>& tp);
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Constraints: zoned_­time is constructible from the return type of traits​::​locate_­zone(name) and tp.
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Effects: Equivalent to construction with {traits​::​locate_­zone(name), tp}.
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zoned_time(TimeZonePtr z, const local_time<Duration>& tp, choose c);
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Constraints: is_convertible_v< decltype(declval<TimeZonePtr&>()->to_sys(local_time<Duration>{}, choose::earliest)), sys_time<duration>> is true.
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Preconditions: z refers to a time zone.
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Effects: Initializes zone_­ with std​::​move(z) and tp_­ with zone_­->to_­sys(tp, c).
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zoned_time(string_view name, const local_time<Duration>& tp, choose c);
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Constraints: zoned_­time is constructible from the return type of traits​::​locate_­zone(name), local_­time<Duration>, and choose.
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Effects: Equivalent to construction with {traits​::​locate_­zone(name), tp, c}.
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template<class Duration2, class TimeZonePtr2> zoned_time(TimeZonePtr z, const zoned_time<Duration2, TimeZonePtr2>& y);
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Constraints: is_­convertible_­v<sys_­time<Duration2>, sys_­time<Duration>> is true.
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Preconditions: z refers to a valid time zone.
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Effects: Initializes zone_­ with std​::​move(z) and tp_­ with y.tp_­.
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template<class Duration2, class TimeZonePtr2> zoned_time(TimeZonePtr z, const zoned_time<Duration2, TimeZonePtr2>& y, choose);
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Constraints: is_­convertible_­v<sys_­time<Duration2>, sys_­time<Duration>> is true.
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Preconditions: z refers to a valid time zone.
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Effects: Equivalent to construction with {z, y}.
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[Note 1:
The choose parameter has no effect.
— end note]
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template<class Duration2, class TimeZonePtr2> zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& y);
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Constraints: zoned_­time is constructible from the return type of traits​::​locate_­zone(name) and the type zoned_­time<Duration2, TimeZonePtr2>.
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Effects: Equivalent to construction with {traits​::​locate_­zone(name), y}.
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template<class Duration2, class TimeZonePtr2> zoned_time(string_view name, const zoned_time<Duration2, TimeZonePtr2>& y, choose c);
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Constraints: zoned_­time is constructible from the return type of traits​::​locate_­zone(name), the type zoned_­time<Duration2, TimeZonePtr2>, and the type choose.
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Effects: Equivalent to construction with {traits​::​locate_­zone(name), y, c}.
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[Note 2:
The choose parameter has no effect.
— end note]

27.11.7.3 Member functions [time.zone.zonedtime.members]

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zoned_time& operator=(const sys_time<Duration>& st);
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Effects: After assignment, get_­sys_­time() == st.
This assignment has no effect on the return value of get_­time_­zone().
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Returns: *this.
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zoned_time& operator=(const local_time<Duration>& lt);
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Effects: After assignment, get_­local_­time() == lt.
This assignment has no effect on the return value of get_­time_­zone().
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Returns: *this.
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operator sys_time<duration>() const;
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Returns: get_­sys_­time().
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explicit operator local_time<duration>() const;
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Returns: get_­local_­time().
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TimeZonePtr get_time_zone() const;
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Returns: zone_­.
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local_time<duration> get_local_time() const;
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Returns: zone_­->to_­local(tp_­).
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sys_time<duration> get_sys_time() const;
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Returns: tp_­.
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sys_info get_info() const;
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Returns: zone_­->get_­info(tp_­).

27.11.7.4 Non-member functions [time.zone.zonedtime.nonmembers]

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template<class Duration1, class Duration2, class TimeZonePtr> bool operator==(const zoned_time<Duration1, TimeZonePtr>& x, const zoned_time<Duration2, TimeZonePtr>& y);
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Returns: x.zone_­ == y.zone_­ && x.tp_­ == y.tp_­.
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template<class charT, class traits, class Duration, class TimeZonePtr> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const zoned_time<Duration, TimeZonePtr>& t);
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Effects: Streams the value returned from t.get_­local_­time() to os using the format "%F %T %Z".
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Returns: os.