27 Time library [time]

27.11 Time zones [time.zone]

27.11.5 Class time_­zone [time.zone.timezone]

27.11.5.1 Overview [time.zone.overview]

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

    // unspecified additional constructors

    string_view name() const noexcept;

    template<class Duration> sys_info   get_info(const sys_time<Duration>& st)   const;
    template<class Duration> local_info get_info(const local_time<Duration>& tp) const;

    template<class Duration>
      sys_time<common_type_t<Duration, seconds>>
        to_sys(const local_time<Duration>& tp) const;

    template<class Duration>
      sys_time<common_type_t<Duration, seconds>>
        to_sys(const local_time<Duration>& tp, choose z) const;

    template<class Duration>
      local_time<common_type_t<Duration, seconds>>
        to_local(const sys_time<Duration>& tp) const;
  };
}
1
#
A time_­zone represents all time zone transitions for a specific geographic area.
time_­zone construction is unspecified, and performed as part of database initialization.
[ Note
:
const time_­zone objects can be accessed via functions such as locate_­zone.
— end note
 ]

27.11.5.2 Member functions [time.zone.members]

🔗
string_view name() const noexcept;
1
#
Returns: The name of the time_­zone.
2
#
[ Example
:
"America/New_­York".
— end example
 ]
🔗
template<class Duration> sys_info get_info(const sys_time<Duration>& st) const;
3
#
Returns: A sys_­info i for which st is in the range [i.begin, i.end).
🔗
template<class Duration> local_info get_info(const local_time<Duration>& tp) const;
4
#
Returns: A local_­info for tp.
🔗
template<class Duration> sys_time<common_type_t<Duration, seconds>> to_sys(const local_time<Duration>& tp) const;
5
#
Returns: A sys_­time that is at least as fine as seconds, and will be finer if the argument tp has finer precision.
This sys_­time is the UTC equivalent of tp according to the rules of this time_­zone.
6
#
Throws: If the conversion from tp to a sys_­time is ambiguous, throws ambiguous_­local_­time.
If the tp represents a non-existent time between two UTC time_­points, throws nonexistent_­local_­time.
🔗
template<class Duration> sys_time<common_type_t<Duration, seconds>> to_sys(const local_time<Duration>& tp, choose z) const;
7
#
Returns: A sys_­time that is at least as fine as seconds, and will be finer if the argument tp has finer precision.
This sys_­time is the UTC equivalent of tp according to the rules of this time_­zone.
If the conversion from tp to a sys_­time is ambiguous, returns the earlier sys_­time if z == choose​::​earliest, and returns the later sys_­time if z == choose​::​latest.
If the tp represents a non-existent time between two UTC time_­points, then the two UTC time_­points will be the same, and that UTC time_­point will be returned.
🔗
template<class Duration> local_time<common_type_t<Duration, seconds>> to_local(const sys_time<Duration>& tp) const;
8
#
Returns: The local_­time associated with tp and this time_­zone.

27.11.5.3 Non-member functions [time.zone.nonmembers]

🔗
bool operator==(const time_zone& x, const time_zone& y) noexcept;
1
#
Returns: x.name() == y.name().
🔗
strong_ordering operator<=>(const time_zone& x, const time_zone& y) noexcept;
2
#
Returns: x.name() <=> y.name().