From Jason Turner

[time]

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tmp/tmpu4zciyft/{from.md → to.md} RENAMED
@@ -19,16 +19,14 @@ summarized in [[time.summary]].
19
  | [[time.hms]] | Class template `hh_mm_ss` | |
20
  | [[time.12]] | 12/24 hour functions | |
21
  | [[time.zone]] | Time zones | |
22
  | [[time.format]] | Formatting | |
23
  | [[time.parse]] | Parsing | |
 
24
  | [[ctime.syn]] | C library time utilities | `<ctime>` |
25
 
26
 
27
- Let *`STATICALLY-WIDEN`*`<charT>("...")` be `"..."` if `charT` is `char`
28
- and `L"..."` if `charT` is `wchar_t`.
29
-
30
  ## Header `<chrono>` synopsis <a id="time.syn">[[time.syn]]</a>
31
 
32
  ``` cpp
33
  #include <compare> // see [compare.syn]
34
 
@@ -907,10 +905,35 @@ namespace std::inline literals::inline chrono_literals {
907
  }
908
 
909
  namespace std::chrono {
910
  using namespace literals::chrono_literals;
911
  }
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
912
  ```
913
 
914
  ## *Cpp17Clock* requirements <a id="time.clock.req">[[time.clock.req]]</a>
915
 
916
  A clock is a bundle consisting of a `duration`, a `time_point`, and a
@@ -928,11 +951,11 @@ calls occur before `C1::time_point::max()`.
928
 
929
  [*Note 2*: The relative difference in durations between those reported
930
  by a given clock and the SI definition is a measure of the quality of
931
  implementation. — *end note*]
932
 
933
- A type `TC` meets the *Cpp17TrivialClock* requirements if:
934
 
935
  - `TC` meets the *Cpp17Clock* requirements,
936
  - the types `TC::rep`, `TC::duration`, and `TC::time_point` meet the
937
  *Cpp17EqualityComparable* ([[cpp17.equalitycomparable]]) and
938
  *Cpp17LessThanComparable* ([[cpp17.lessthancomparable]]) and
@@ -1085,11 +1108,11 @@ as a rational constant using the template `ratio`.
1085
  namespace std::chrono {
1086
  template<class Rep, class Period = ratio<1>>
1087
  class duration {
1088
  public:
1089
  using rep = Rep;
1090
- using period = typename Period::type;
1091
 
1092
  private:
1093
  rep rep_; // exposition only
1094
 
1095
  public:
@@ -1138,13 +1161,14 @@ If `Period` is not a specialization of `ratio`, the program is
1138
  ill-formed. If `Period::num` is not positive, the program is ill-formed.
1139
 
1140
  Members of `duration` do not throw exceptions other than those thrown by
1141
  the indicated operations on their representations.
1142
 
1143
- The defaulted copy constructor of duration shall be a constexpr function
1144
- if and only if the required initialization of the member `rep_` for copy
1145
- and move, respectively, would be constexpr-suitable [[dcl.constexpr]].
 
1146
 
1147
  [*Example 1*:
1148
 
1149
  ``` cpp
1150
  duration<long, ratio<60>> d0; // holds a count of minutes using a long
@@ -1169,11 +1193,11 @@ template<class Rep2>
1169
 
1170
  [*Example 1*:
1171
 
1172
  ``` cpp
1173
  duration<int, milli> d(3); // OK
1174
- duration<int, milli> d(3.5); // error
1175
  ```
1176
 
1177
  — *end example*]
1178
 
1179
  *Effects:* Initializes `rep_` with `r`.
@@ -1708,12 +1732,12 @@ namespace std::chrono {
1708
  template<class Clock, class Duration = typename Clock::duration>
1709
  class time_point {
1710
  public:
1711
  using clock = Clock;
1712
  using duration = Duration;
1713
- using rep = typename duration::rep;
1714
- using period = typename duration::period;
1715
 
1716
  private:
1717
  duration d_; // exposition only
1718
 
1719
  public:
@@ -2992,11 +3016,11 @@ the above list, there is a unique best expression.
2992
  *Returns:* The best well-formed clock time conversion expression in the
2993
  above list.
2994
 
2995
  ## The civil calendar <a id="time.cal">[[time.cal]]</a>
2996
 
2997
- ### In general <a id="time.cal.general">[[time.cal.general]]</a>
2998
 
2999
  The types in [[time.cal]] describe the civil (Gregorian) calendar and
3000
  its relationship to `sys_days` and `local_days`.
3001
 
3002
  ### Class `last_spec` <a id="time.cal.last">[[time.cal.last]]</a>
@@ -5628,12 +5652,11 @@ The year, month, and day are accepted in any of the following 3 orders:
5628
  year/month/day
5629
  month/day/year
5630
  day/month/year
5631
  ```
5632
 
5633
- Anywhere a `day` is required, any of the following can also be
5634
- specified:
5635
 
5636
  ``` cpp
5637
  last
5638
  weekday[i]
5639
  weekday[last]
@@ -6181,11 +6204,11 @@ hour. Otherwise, returns the 24-hour equivalent of `h` in the range
6181
  \[`12h`, `23h`\], assuming `h` represents a post meridiem hour. If `h`
6182
  is not in the range \[`1h`, `12h`\], the value returned is unspecified.
6183
 
6184
  ## Time zones <a id="time.zone">[[time.zone]]</a>
6185
 
6186
- ### In general <a id="time.zone.general">[[time.zone.general]]</a>
6187
 
6188
  [[time.zone]] describes an interface for accessing the IANA Time Zone
6189
  Database that interoperates with `sys_time` and `local_time`. This
6190
  interface provides time zone support to both the civil calendar types
6191
  [[time.cal]] and to user-defined calendars.
@@ -7193,11 +7216,11 @@ database when initialized.
7193
 
7194
  [*Example 1*:
7195
 
7196
  ``` cpp
7197
  for (auto& l : get_tzdb().leap_seconds)
7198
- if (l <= 2018y/March/17d)
7199
  cout << l.date() << ": " << l.value() << '\n';
7200
  ```
7201
 
7202
  Produces the output:
7203
 
@@ -7446,11 +7469,11 @@ function, defined as
7446
  - the locale passed to the formatting function if any, otherwise
7447
  - the global locale.
7448
 
7449
  Each conversion specifier *conversion-spec* is replaced by appropriate
7450
  characters as described in [[time.format.spec]]; the formats specified
7451
- in ISO 8601:2004 shall be used where so described. Some of the
7452
  conversion specifiers depend on the formatting locale. If the string
7453
  literal encoding is a Unicode encoding form and the locale is among an
7454
  *implementation-defined* set of locales, each replacement that depends
7455
  on the locale is performed as if the replacement character sequence is
7456
  converted to the string literal encoding. If the formatted object does
@@ -7505,16 +7528,16 @@ day elapsed since midnight.
7505
  | `%C` | The year divided by 100 using floored division. If the result is a single decimal digit, it is prefixed with `0`. The modified command `%EC` produces the locale's alternative representation of the century. |
7506
  | `%d` | The day of month as a decimal number. If the result is a single decimal digit, it is prefixed with `0`. The modified command `%Od` produces the locale's alternative representation. |
7507
  | `%D` | Equivalent to `%m/%d/%y`. |
7508
  | `%e` | The day of month as a decimal number. If the result is a single decimal digit, it is prefixed with a space. The modified command `%Oe` produces the locale's alternative representation. |
7509
  | `%F` | Equivalent to `%Y-%m-%d`. |
7510
- | `%g` | The last two decimal digits of the ISO week-based year. If the result is a single digit it is prefixed by `0`. |
7511
- | `%G` | The ISO week-based year as a decimal number. If the result is less than four digits it is left-padded with `0` to four digits. |
7512
  | `%h` | Equivalent to `%b`. |
7513
  | `%H` | The hour (24-hour clock) as a decimal number. If the result is a single digit, it is prefixed with `0`. The modified command `%OH` produces the locale's alternative representation. |
7514
  | `%I` | The hour (12-hour clock) as a decimal number. If the result is a single digit, it is prefixed with `0`. The modified command `%OI` produces the locale's alternative representation. |
7515
- | `%j` | If the type being formatted is a specialization of `duration`, the decimal number of `days` without padding. Otherwise, the day of the year as a decimal number. Jan 1 is `001`. If the result is less than three digits, it is left-padded with `0` to three digits. |
7516
  | `%m` | The month as a decimal number. Jan is `01`. If the result is a single digit, it is prefixed with `0`. The modified command `%Om` produces the locale's alternative representation. |
7517
  | `%M` | The minute as a decimal number. If the result is a single digit, it is prefixed with `0`. The modified command `%OM` produces the locale's alternative representation. |
7518
  | `%n` | A new-line character. |
7519
  | `%p` | The locale's equivalent of the AM/PM designations associated with a 12-hour clock. |
7520
  | `%q` | The duration's unit suffix as specified in [[time.duration.io]]. |
@@ -7522,38 +7545,58 @@ day elapsed since midnight.
7522
  | `%r` | The locale's 12-hour clock time. |
7523
  | `%R` | Equivalent to `%H:%M`. |
7524
  | `%S` | Seconds as a decimal number. If the number of seconds is less than `10`, the result is prefixed with `0`. If the precision of the input cannot be exactly represented with seconds, then the format is a decimal floating-point number with a fixed format and a precision matching that of the precision of the input (or to a microseconds precision if the conversion to floating-point decimal seconds cannot be made within 18 fractional digits). The character for the decimal point is localized according to the locale. The modified command `%OS` produces the locale's alternative representation. |
7525
  | `%t` | A horizontal-tab character. |
7526
  | `%T` | Equivalent to `%H:%M:%S`. |
7527
- | `%u` | The ISO weekday as a decimal number (`1`-`7`), where Monday is `1`. The modified command `%Ou` produces the locale's alternative representation. |
7528
  | `%U` | The week number of the year as a decimal number. The first Sunday of the year is the first day of week `01`. Days of the same year prior to that are in week `00`. If the result is a single digit, it is prefixed with `0`. The modified command `%OU` produces the locale's alternative representation. |
7529
- | `%V` | The ISO week-based week number as a decimal number. If the result is a single digit, it is prefixed with `0`. The modified command `%OV` produces the locale's alternative representation. |
7530
  | `%w` | The weekday as a decimal number (`0`-`6`), where Sunday is `0`. The modified command `%Ow` produces the locale's alternative representation. |
7531
  | `%W` | The week number of the year as a decimal number. The first Monday of the year is the first day of week `01`. Days of the same year prior to that are in week `00`. If the result is a single digit, it is prefixed with `0`. The modified command `%OW` produces the locale's alternative representation. |
7532
  | `%x` | The locale's date representation. The modified command `%Ex` produces the locale's alternate date representation. |
7533
  | `%X` | The locale's time representation. The modified command `%EX` produces the locale's alternate time representation. |
7534
- | `%y` | The last two decimal digits of the year. If the result is a single digit it is prefixed by `0`. The modified command `%Oy` produces the locale's alternative representation. The modified command `%Ey` produces the locale's alternative representation of offset from `%EC` (year only). |
7535
- | `%Y` | The year as a decimal number. If the result is less than four digits it is left-padded with `0` to four digits. The modified command `%EY` produces the locale's alternative full year representation. |
7536
- | `%z` | The offset from UTC in the ISO 8601:2004 format. For example `-0430` refers to 4 hours 30 minutes behind UTC. If the offset is zero, `+0000` is used. The modified commands `%Ez` and `%Oz` insert a `:` between the hours and minutes: `-04:30`. If the offset information is not available, an exception of type `format_error` is thrown. |
7537
  | `%Z` | The time zone abbreviation. If the time zone abbreviation is not available, an exception of type `format_error` is thrown. |
7538
  | `%%` | A `%` character. |
7539
 
7540
 
7541
- If the *chrono-specs* is omitted, the chrono object is formatted as if
7542
- by streaming it to `basic_ostringstream<charT> os` with the formatting
7543
- locale imbued and copying `os.str()` through the output iterator of the
7544
- context with additional padding and adjustments as specified by the
7545
- format specifiers.
 
7546
 
7547
  [*Example 3*:
7548
 
7549
  ``` cpp
7550
  string s = format("{:=>8}", 42ms); // value of s is "====42ms"
7551
  ```
7552
 
7553
  — *end example*]
7554
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7555
  ``` cpp
7556
  template<class Duration, class charT>
7557
  struct formatter<chrono::sys_time<Duration>, charT>;
7558
  ```
7559
 
@@ -7648,23 +7691,24 @@ template<class Duration, class charT>
7648
  ```
7649
 
7650
  Let `f` be a *`local-time-format-t`*`<Duration>` object passed to
7651
  `formatter::format`.
7652
 
7653
- *Remarks:* If `%Z` is used, it is replaced with `*f.abbrev` if
7654
- `f.abbrev` is not a null pointer value. If `%Z` is used and `f.abbrev`
7655
- is a null pointer value, an exception of type `format_error` is thrown.
7656
- If `%z` (or a modified variant of `%z`) is used, it is formatted with
7657
- the value of `*f.offset_sec` if `f.offset_sec` is not a null pointer
7658
- value. If `%z` (or a modified variant of `%z`) is used and
7659
- `f.offset_sec` is a null pointer value, then an exception of type
7660
- `format_error` is thrown.
 
7661
 
7662
  ``` cpp
7663
  template<class Duration, class TimeZonePtr, class charT>
7664
  struct formatter<chrono::zoned_time<Duration, TimeZonePtr>, charT>
7665
- : formatter<chrono::local-time-format-t<Duration>, charT> {
7666
  template<class FormatContext>
7667
  typename FormatContext::iterator
7668
  format(const chrono::zoned_time<Duration, TimeZonePtr>& tp, FormatContext& ctx) const;
7669
  };
7670
  ```
@@ -7677,18 +7721,18 @@ template<class FormatContext>
7677
 
7678
  *Effects:* Equivalent to:
7679
 
7680
  ``` cpp
7681
  sys_info info = tp.get_info();
7682
- return formatter<chrono::local-time-format-t<Duration>, charT>::
7683
  format({tp.get_local_time(), &info.abbrev, &info.offset}, ctx);
7684
  ```
7685
 
7686
  ## Parsing <a id="time.parse">[[time.parse]]</a>
7687
 
7688
  Each `parse` overload specified in this subclause calls `from_stream`
7689
- unqualified, so as to enable argument dependent lookup
7690
  [[basic.lookup.argdep]]. In the following paragraphs, let `is` denote an
7691
  object of type `basic_istream<charT, traits>` and let `I` be
7692
  `basic_istream<charT, traits>&`, where `charT` and `traits` are template
7693
  parameters in that context.
7694
 
@@ -7854,28 +7898,28 @@ complete duration, time point, or calendrical data structure,
7854
  | `%C` | The century as a decimal number. The modified command `%*N*C` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%EC` interprets the locale's alternative representation of the century. |
7855
  | `%d` | The day of the month as a decimal number. The modified command `%*N*d` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%Od` interprets the locale's alternative representation of the day of the month. |
7856
  | `%D` | Equivalent to `%m/%d/%y`. |
7857
  | `%e` | Equivalent to `%d` and can be modified like `%d`. |
7858
  | `%F` | Equivalent to `%Y-%m-%d`. If modified with a width `*N*`, the width is applied to only `%Y`. |
7859
- | `%g` | The last two decimal digits of the ISO week-based year. The modified command `%*N*g` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. |
7860
- | `%G` | The ISO week-based year as a decimal number. The modified command `%*N*G` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 4. Leading zeroes are permitted but not required. |
7861
  | `%h` | Equivalent to `%b`. |
7862
  | `%H` | The hour (24-hour clock) as a decimal number. The modified command `%*N*H` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%OH` interprets the locale's alternative representation. |
7863
  | `%I` | The hour (12-hour clock) as a decimal number. The modified command `%*N*I` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%OI` interprets the locale's alternative representation. |
7864
- | `%j` | If the type being parsed is a specialization of `duration`, a decimal number of `days`. Otherwise, the day of the year as a decimal number. Jan 1 is `1`. In either case, the modified command `%*N*j` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 3. Leading zeroes are permitted but not required. |
7865
- | `%m` | The month as a decimal number. Jan is `1`. The modified command `%*N*m` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%Om` interprets the locale's alternative representation. |
7866
  | `%M` | The minutes as a decimal number. The modified command `%*N*M` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%OM` interprets the locale's alternative representation. |
7867
  | `%n` | Matches one whitespace character. *`%n`, `%t`, and a space can be combined to match a wide range of whitespace patterns. For example, `"%n "` matches one or more whitespace characters, and `"%n%t%t"` matches one to three whitespace characters.* |
7868
  | `%p` | The locale's equivalent of the AM/PM designations associated with a 12-hour clock. |
7869
  | `%r` | The locale's 12-hour clock time. |
7870
  | `%R` | Equivalent to `%H:%M`. |
7871
  | `%S` | The seconds as a decimal number. The modified command `%*N*S` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2 if the input time has a precision convertible to seconds. Otherwise the default width is determined by the decimal precision of the input and the field is interpreted as a `long double` in a fixed format. If encountered, the locale determines the decimal point character. Leading zeroes are permitted but not required. The modified command `%OS` interprets the locale's alternative representation. |
7872
  | `%t` | Matches zero or one whitespace characters. |
7873
  | `%T` | Equivalent to `%H:%M:%S`. |
7874
- | `%u` | The ISO weekday as a decimal number (`1`-`7`), where Monday is `1`. The modified command `%*N*u` specifies the maximum number of characters to read. If `*N*` is not specified, the default is `1`. Leading zeroes are permitted but not required. |
7875
  | `%U` | The week number of the year as a decimal number. The first Sunday of the year is the first day of week `01`. Days of the same year prior to that are in week `00`. The modified command `%*N*U` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%OU` interprets the locale's alternative representation. |
7876
- | `%V` | The ISO week-based week number as a decimal number. The modified command `%*N*V` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. |
7877
  | `%w` | The weekday as a decimal number (`0`-`6`), where Sunday is `0`. The modified command `%*N*w` specifies the maximum number of characters to read. If `*N*` is not specified, the default is `1`. Leading zeroes are permitted but not required. The modified command `%Ow` interprets the locale's alternative representation. |
7878
  | `%W` | The week number of the year as a decimal number. The first Monday of the year is the first day of week `01`. Days of the same year prior to that are in week `00`. The modified command `%*N*W` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%OW` interprets the locale's alternative representation. |
7879
  | `%x` | The locale's date representation. The modified command `%Ex` interprets the locale's alternate date representation. |
7880
  | `%X` | The locale's time representation. The modified command `%EX` interprets the locale's alternate time representation. |
7881
  | `%y` | The last two decimal digits of the year. If the century is not otherwise specified (e.g., with `%C`), values in the range {[}`69`, `99`{]} are presumed to refer to the years 1969 to 1999, and values in the range {[}`00`, `68`{]} are presumed to refer to the years 2000 to 2068. The modified command `%*N*y` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified commands `%Ey` and `%Oy` interpret the locale's alternative representation. |
@@ -7883,16 +7927,80 @@ complete duration, time point, or calendrical data structure,
7883
  | `%z` | The offset from UTC in the format `[+|-]hh[mm]`. For example `-0430` refers to 4 hours 30 minutes behind UTC, and `04` refers to 4 hours ahead of UTC. The modified commands `%Ez` and `%Oz` parse a `:` between the hours and minutes and render leading zeroes on the hour field optional: `[+|-]h[h][:mm]`. For example `-04:30` refers to 4 hours 30 minutes behind UTC, and `4` refers to 4 hours ahead of UTC. |
7884
  | `%Z` | The time zone abbreviation or name. A single word is parsed. This word can only contain characters from the basic character set [[lex.charset]] that are alphanumeric, or one of `'_'`, `'/'`, `'-'`, or `'+'`. |
7885
  | `%%` | A `%` character is extracted. |
7886
 
7887
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7888
  ## Header `<ctime>` synopsis <a id="ctime.syn">[[ctime.syn]]</a>
7889
 
7890
  ``` cpp
 
 
7891
  #define NULL see [support.types.nullptr]
7892
  #define CLOCKS_PER_SEC see below
7893
  #define TIME_UTC see below
 
 
 
7894
 
7895
  namespace std {
7896
  using size_t = see [support.types.layout];
7897
  using clock_t = see below;
7898
  using time_t = see below;
@@ -7901,38 +8009,40 @@ namespace std {
7901
  struct tm;
7902
 
7903
  clock_t clock();
7904
  double difftime(time_t time1, time_t time0);
7905
  time_t mktime(tm* timeptr);
 
7906
  time_t time(time_t* timer);
7907
  int timespec_get(timespec* ts, int base);
7908
- char* asctime(const tm* timeptr);
7909
- char* ctime(const time_t* timer);
7910
  tm* gmtime(const time_t* timer);
 
7911
  tm* localtime(const time_t* timer);
 
7912
  size_t strftime(char* s, size_t maxsize, const char* format, const tm* timeptr);
7913
  }
7914
  ```
7915
 
7916
  The contents of the header `<ctime>` are the same as the C standard
7917
  library header `<time.h>`.[^1]
7918
 
7919
- The functions `asctime`, `ctime`, `gmtime`, and `localtime` are not
7920
- required to avoid data races [[res.on.data.races]].
7921
 
7922
- See also: ISO C 7.27
7923
 
7924
  <!-- Link reference definitions -->
7925
  [basic.lookup.argdep]: basic.md#basic.lookup.argdep
7926
  [cpp17.equalitycomparable]: #cpp17.equalitycomparable
7927
  [cpp17.lessthancomparable]: #cpp17.lessthancomparable
7928
  [ctime.syn]: #ctime.syn
7929
  [dcl.constexpr]: dcl.md#dcl.constexpr
7930
  [filesystems]: input.md#filesystems
7931
- [format.formatter]: utilities.md#format.formatter
7932
- [format.string]: utilities.md#format.string
7933
- [formatter.requirements]: utilities.md#formatter.requirements
7934
  [intro.multithread]: basic.md#intro.multithread
7935
  [lex.charset]: lex.md#lex.charset
7936
  [meta.rqmts]: meta.md#meta.rqmts
7937
  [numeric.requirements]: numerics.md#numeric.requirements
7938
  [over.ics.rank]: over.md#over.ics.rank
@@ -8050,10 +8160,11 @@ See also: ISO C 7.27
8050
  [time.duration.observer]: #time.duration.observer
8051
  [time.duration.special]: #time.duration.special
8052
  [time.format]: #time.format
8053
  [time.format.spec]: #time.format.spec
8054
  [time.general]: #time.general
 
8055
  [time.hms]: #time.hms
8056
  [time.hms.members]: #time.hms.members
8057
  [time.hms.nonmembers]: #time.hms.nonmembers
8058
  [time.hms.overview]: #time.hms.overview
8059
  [time.hms.width]: #time.hms.width
@@ -8104,9 +8215,10 @@ See also: ISO C 7.27
8104
  [time.zone.zonedtime.ctor]: #time.zone.zonedtime.ctor
8105
  [time.zone.zonedtime.members]: #time.zone.zonedtime.members
8106
  [time.zone.zonedtime.nonmembers]: #time.zone.zonedtime.nonmembers
8107
  [time.zone.zonedtime.overview]: #time.zone.zonedtime.overview
8108
  [time.zone.zonedtraits]: #time.zone.zonedtraits
 
8109
 
8110
  [^1]: `strftime` supports the C conversion specifiers `C`, `D`, `e`,
8111
  `F`, `g`, `G`, `h`, `r`, `R`, `t`, `T`, `u`, `V`, and `z`, and the
8112
  modifiers `E` and `O`.
 
19
  | [[time.hms]] | Class template `hh_mm_ss` | |
20
  | [[time.12]] | 12/24 hour functions | |
21
  | [[time.zone]] | Time zones | |
22
  | [[time.format]] | Formatting | |
23
  | [[time.parse]] | Parsing | |
24
+ | [[time.hash]] | Hash support | |
25
  | [[ctime.syn]] | C library time utilities | `<ctime>` |
26
 
27
 
 
 
 
28
  ## Header `<chrono>` synopsis <a id="time.syn">[[time.syn]]</a>
29
 
30
  ``` cpp
31
  #include <compare> // see [compare.syn]
32
 
 
905
  }
906
 
907
  namespace std::chrono {
908
  using namespace literals::chrono_literals;
909
  }
910
+
911
+ namespace std {
912
+ // [time.hash], hash support
913
+ template<class T> struct hash;
914
+ template<class Rep, class Period> struct hash<chrono::duration<Rep, Period>>;
915
+ template<class Clock, class Duration> struct hash<chrono::time_point<Clock, Duration>>;
916
+ template<> struct hash<chrono::day>;
917
+ template<> struct hash<chrono::month>;
918
+ template<> struct hash<chrono::year>;
919
+ template<> struct hash<chrono::weekday>;
920
+ template<> struct hash<chrono::weekday_indexed>;
921
+ template<> struct hash<chrono::weekday_last>;
922
+ template<> struct hash<chrono::month_day>;
923
+ template<> struct hash<chrono::month_day_last>;
924
+ template<> struct hash<chrono::month_weekday>;
925
+ template<> struct hash<chrono::month_weekday_last>;
926
+ template<> struct hash<chrono::year_month>;
927
+ template<> struct hash<chrono::year_month_day>;
928
+ template<> struct hash<chrono::year_month_day_last>;
929
+ template<> struct hash<chrono::year_month_weekday>;
930
+ template<> struct hash<chrono::year_month_weekday_last>;
931
+ template<class Duration, class TimeZonePtr>
932
+ struct hash<chrono::zoned_time<Duration, TimeZonePtr>>;
933
+ template<> struct hash<chrono::leap_second>;
934
+ }
935
  ```
936
 
937
  ## *Cpp17Clock* requirements <a id="time.clock.req">[[time.clock.req]]</a>
938
 
939
  A clock is a bundle consisting of a `duration`, a `time_point`, and a
 
951
 
952
  [*Note 2*: The relative difference in durations between those reported
953
  by a given clock and the SI definition is a measure of the quality of
954
  implementation. — *end note*]
955
 
956
+ A type `TC` meets the requirements if
957
 
958
  - `TC` meets the *Cpp17Clock* requirements,
959
  - the types `TC::rep`, `TC::duration`, and `TC::time_point` meet the
960
  *Cpp17EqualityComparable* ([[cpp17.equalitycomparable]]) and
961
  *Cpp17LessThanComparable* ([[cpp17.lessthancomparable]]) and
 
1108
  namespace std::chrono {
1109
  template<class Rep, class Period = ratio<1>>
1110
  class duration {
1111
  public:
1112
  using rep = Rep;
1113
+ using period = Period::type;
1114
 
1115
  private:
1116
  rep rep_; // exposition only
1117
 
1118
  public:
 
1161
  ill-formed. If `Period::num` is not positive, the program is ill-formed.
1162
 
1163
  Members of `duration` do not throw exceptions other than those thrown by
1164
  the indicated operations on their representations.
1165
 
1166
+ The defaulted copy constructor of `duration` shall be a constexpr
1167
+ function if and only if the required initialization of the member `rep_`
1168
+ for copy and move, respectively, would be constexpr-suitable
1169
+ [[dcl.constexpr]].
1170
 
1171
  [*Example 1*:
1172
 
1173
  ``` cpp
1174
  duration<long, ratio<60>> d0; // holds a count of minutes using a long
 
1193
 
1194
  [*Example 1*:
1195
 
1196
  ``` cpp
1197
  duration<int, milli> d(3); // OK
1198
+ duration<int, milli> d2(3.5); // error
1199
  ```
1200
 
1201
  — *end example*]
1202
 
1203
  *Effects:* Initializes `rep_` with `r`.
 
1732
  template<class Clock, class Duration = typename Clock::duration>
1733
  class time_point {
1734
  public:
1735
  using clock = Clock;
1736
  using duration = Duration;
1737
+ using rep = duration::rep;
1738
+ using period = duration::period;
1739
 
1740
  private:
1741
  duration d_; // exposition only
1742
 
1743
  public:
 
3016
  *Returns:* The best well-formed clock time conversion expression in the
3017
  above list.
3018
 
3019
  ## The civil calendar <a id="time.cal">[[time.cal]]</a>
3020
 
3021
+ ### General <a id="time.cal.general">[[time.cal.general]]</a>
3022
 
3023
  The types in [[time.cal]] describe the civil (Gregorian) calendar and
3024
  its relationship to `sys_days` and `local_days`.
3025
 
3026
  ### Class `last_spec` <a id="time.cal.last">[[time.cal.last]]</a>
 
5652
  year/month/day
5653
  month/day/year
5654
  day/month/year
5655
  ```
5656
 
5657
+ Anywhere a `day` is needed, any of the following can also be specified:
 
5658
 
5659
  ``` cpp
5660
  last
5661
  weekday[i]
5662
  weekday[last]
 
6204
  \[`12h`, `23h`\], assuming `h` represents a post meridiem hour. If `h`
6205
  is not in the range \[`1h`, `12h`\], the value returned is unspecified.
6206
 
6207
  ## Time zones <a id="time.zone">[[time.zone]]</a>
6208
 
6209
+ ### General <a id="time.zone.general">[[time.zone.general]]</a>
6210
 
6211
  [[time.zone]] describes an interface for accessing the IANA Time Zone
6212
  Database that interoperates with `sys_time` and `local_time`. This
6213
  interface provides time zone support to both the civil calendar types
6214
  [[time.cal]] and to user-defined calendars.
 
7216
 
7217
  [*Example 1*:
7218
 
7219
  ``` cpp
7220
  for (auto& l : get_tzdb().leap_seconds)
7221
+ if (l <= sys_days{2018y/March/17d})
7222
  cout << l.date() << ": " << l.value() << '\n';
7223
  ```
7224
 
7225
  Produces the output:
7226
 
 
7469
  - the locale passed to the formatting function if any, otherwise
7470
  - the global locale.
7471
 
7472
  Each conversion specifier *conversion-spec* is replaced by appropriate
7473
  characters as described in [[time.format.spec]]; the formats specified
7474
+ in ISO 8601-1:2019 shall be used where so described. Some of the
7475
  conversion specifiers depend on the formatting locale. If the string
7476
  literal encoding is a Unicode encoding form and the locale is among an
7477
  *implementation-defined* set of locales, each replacement that depends
7478
  on the locale is performed as if the replacement character sequence is
7479
  converted to the string literal encoding. If the formatted object does
 
7528
  | `%C` | The year divided by 100 using floored division. If the result is a single decimal digit, it is prefixed with `0`. The modified command `%EC` produces the locale's alternative representation of the century. |
7529
  | `%d` | The day of month as a decimal number. If the result is a single decimal digit, it is prefixed with `0`. The modified command `%Od` produces the locale's alternative representation. |
7530
  | `%D` | Equivalent to `%m/%d/%y`. |
7531
  | `%e` | The day of month as a decimal number. If the result is a single decimal digit, it is prefixed with a space. The modified command `%Oe` produces the locale's alternative representation. |
7532
  | `%F` | Equivalent to `%Y-%m-%d`. |
7533
+ | `%g` | The last two decimal digits of the calendar year as specified in ISO 8601-1:2019 for the week calendar. If the result is a single digit it is prefixed by `0`. |
7534
+ | `%G` | The calendar year as a decimal number, as specified in ISO 8601-1:2019 for the week calendar. If the result is less than four digits it is left-padded with `0` to four digits. |
7535
  | `%h` | Equivalent to `%b`. |
7536
  | `%H` | The hour (24-hour clock) as a decimal number. If the result is a single digit, it is prefixed with `0`. The modified command `%OH` produces the locale's alternative representation. |
7537
  | `%I` | The hour (12-hour clock) as a decimal number. If the result is a single digit, it is prefixed with `0`. The modified command `%OI` produces the locale's alternative representation. |
7538
+ | `%j` | If the type being formatted is a specialization of `duration`, the decimal number of `days` without padding. Otherwise, the day of the year as a decimal number. January 1 is `001`. If the result is less than three digits, it is left-padded with `0` to three digits. |
7539
  | `%m` | The month as a decimal number. Jan is `01`. If the result is a single digit, it is prefixed with `0`. The modified command `%Om` produces the locale's alternative representation. |
7540
  | `%M` | The minute as a decimal number. If the result is a single digit, it is prefixed with `0`. The modified command `%OM` produces the locale's alternative representation. |
7541
  | `%n` | A new-line character. |
7542
  | `%p` | The locale's equivalent of the AM/PM designations associated with a 12-hour clock. |
7543
  | `%q` | The duration's unit suffix as specified in [[time.duration.io]]. |
 
7545
  | `%r` | The locale's 12-hour clock time. |
7546
  | `%R` | Equivalent to `%H:%M`. |
7547
  | `%S` | Seconds as a decimal number. If the number of seconds is less than `10`, the result is prefixed with `0`. If the precision of the input cannot be exactly represented with seconds, then the format is a decimal floating-point number with a fixed format and a precision matching that of the precision of the input (or to a microseconds precision if the conversion to floating-point decimal seconds cannot be made within 18 fractional digits). The character for the decimal point is localized according to the locale. The modified command `%OS` produces the locale's alternative representation. |
7548
  | `%t` | A horizontal-tab character. |
7549
  | `%T` | Equivalent to `%H:%M:%S`. |
7550
+ | `%u` | The calendar day of week as a decimal number (`1`-`7`), as specified in ISO 8601-1:2019, where Monday is `1`. The modified command `%Ou` produces the locale's alternative representation. |
7551
  | `%U` | The week number of the year as a decimal number. The first Sunday of the year is the first day of week `01`. Days of the same year prior to that are in week `00`. If the result is a single digit, it is prefixed with `0`. The modified command `%OU` produces the locale's alternative representation. |
7552
+ | `%V` | The calendar week of year as a decimal number, as specified in ISO 8601-1:2019 for the week calendar. If the result is a single digit, it is prefixed with `0`. The modified command `%OV` produces the locale's alternative representation. |
7553
  | `%w` | The weekday as a decimal number (`0`-`6`), where Sunday is `0`. The modified command `%Ow` produces the locale's alternative representation. |
7554
  | `%W` | The week number of the year as a decimal number. The first Monday of the year is the first day of week `01`. Days of the same year prior to that are in week `00`. If the result is a single digit, it is prefixed with `0`. The modified command `%OW` produces the locale's alternative representation. |
7555
  | `%x` | The locale's date representation. The modified command `%Ex` produces the locale's alternate date representation. |
7556
  | `%X` | The locale's time representation. The modified command `%EX` produces the locale's alternate time representation. |
7557
+ | `%y` | The last two decimal digits of the year. If the result is a single digit, it is prefixed by `0`. The modified command `%Oy` produces the locale's alternative representation. The modified command `%Ey` produces the locale's alternative representation of offset from `%EC` (year only). |
7558
+ | `%Y` | The year as a decimal number. If the result is less than four digits, it is left-padded with `0` to four digits. The modified command `%EY` produces the locale's alternative full year representation. |
7559
+ | `%z` | The offset from UTC as specified in ISO 8601-1:2019, 5.3.4.1. For example `-0430` refers to 4 hours 30 minutes behind UTC. If the offset is zero, `+0000` is used. The modified commands `%Ez` and `%Oz` insert a `:` between the hours and minutes: `-04:30`. If the offset information is not available, an exception of type `format_error` is thrown. |
7560
  | `%Z` | The time zone abbreviation. If the time zone abbreviation is not available, an exception of type `format_error` is thrown. |
7561
  | `%%` | A `%` character. |
7562
 
7563
 
7564
+ Unless otherwise specified, if the *chrono-specs* is omitted, the chrono
7565
+ object is formatted as if by streaming it to
7566
+ `basic_ostringstream<charT> os` with the formatting locale imbued and
7567
+ copying `os.str()` through the output iterator of the context with
7568
+ additional padding and adjustments as specified by the format
7569
+ specifiers.
7570
 
7571
  [*Example 3*:
7572
 
7573
  ``` cpp
7574
  string s = format("{:=>8}", 42ms); // value of s is "====42ms"
7575
  ```
7576
 
7577
  — *end example*]
7578
 
7579
+ For `chrono::duration` the library only provides the following
7580
+ specialization of `enable_nonlocking_formatter_optimization`:
7581
+
7582
+ ``` cpp
7583
+ template<class Rep, class Period>
7584
+ constexpr bool enable_nonlocking_formatter_optimization<
7585
+ chrono::duration<Rep, Period>> =
7586
+ enable_nonlocking_formatter_optimization<Rep>;
7587
+ ```
7588
+
7589
+ For `chrono::zoned_time` the library only provides the following
7590
+ specialization of `enable_nonlocking_formatter_optimization`:
7591
+
7592
+ ``` cpp
7593
+ template<class Duration>
7594
+ constexpr bool enable_nonlocking_formatter_optimization<
7595
+ chrono::zoned_time<Duration, const std::chrono::time_zone*>> = true;
7596
+ ```
7597
+
7598
  ``` cpp
7599
  template<class Duration, class charT>
7600
  struct formatter<chrono::sys_time<Duration>, charT>;
7601
  ```
7602
 
 
7691
  ```
7692
 
7693
  Let `f` be a *`local-time-format-t`*`<Duration>` object passed to
7694
  `formatter::format`.
7695
 
7696
+ *Remarks:* If the *chrono-specs* is omitted, the result is equivalent to
7697
+ using `%F %T %Z` as the *chrono-specs*. If `%Z` is used, it is replaced
7698
+ with `*f.abbrev` if `f.abbrev` is not a null pointer value. If `%Z` is
7699
+ used and `f.abbrev` is a null pointer value, an exception of type
7700
+ `format_error` is thrown. If `%z` (or a modified variant of `%z`) is
7701
+ used, it is formatted with the value of `*f.offset_sec` if
7702
+ `f.offset_sec` is not a null pointer value. If `%z` (or a modified
7703
+ variant of `%z`) is used and `f.offset_sec` is a null pointer value,
7704
+ then an exception of type `format_error` is thrown.
7705
 
7706
  ``` cpp
7707
  template<class Duration, class TimeZonePtr, class charT>
7708
  struct formatter<chrono::zoned_time<Duration, TimeZonePtr>, charT>
7709
+ : formatter<chrono::local-time-format-t<common_type_t<Duration, seconds>>, charT> {
7710
  template<class FormatContext>
7711
  typename FormatContext::iterator
7712
  format(const chrono::zoned_time<Duration, TimeZonePtr>& tp, FormatContext& ctx) const;
7713
  };
7714
  ```
 
7721
 
7722
  *Effects:* Equivalent to:
7723
 
7724
  ``` cpp
7725
  sys_info info = tp.get_info();
7726
+ return formatter<chrono::local-time-format-t<common_type_t<Duration, seconds>>, charT>::
7727
  format({tp.get_local_time(), &info.abbrev, &info.offset}, ctx);
7728
  ```
7729
 
7730
  ## Parsing <a id="time.parse">[[time.parse]]</a>
7731
 
7732
  Each `parse` overload specified in this subclause calls `from_stream`
7733
+ unqualified, so as to enable argument-dependent lookup
7734
  [[basic.lookup.argdep]]. In the following paragraphs, let `is` denote an
7735
  object of type `basic_istream<charT, traits>` and let `I` be
7736
  `basic_istream<charT, traits>&`, where `charT` and `traits` are template
7737
  parameters in that context.
7738
 
 
7898
  | `%C` | The century as a decimal number. The modified command `%*N*C` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%EC` interprets the locale's alternative representation of the century. |
7899
  | `%d` | The day of the month as a decimal number. The modified command `%*N*d` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%Od` interprets the locale's alternative representation of the day of the month. |
7900
  | `%D` | Equivalent to `%m/%d/%y`. |
7901
  | `%e` | Equivalent to `%d` and can be modified like `%d`. |
7902
  | `%F` | Equivalent to `%Y-%m-%d`. If modified with a width `*N*`, the width is applied to only `%Y`. |
7903
+ | `%g` | The last two decimal digits of the calendar year, as specified in ISO 8601-1:2019 for the week calendar. The modified command `%*N*g` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. |
7904
+ | `%G` | The calendar year as a decimal number, as specified in ISO 8601-1:2019 for the week calendar. The modified command `%*N*G` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 4. Leading zeroes are permitted but not required. |
7905
  | `%h` | Equivalent to `%b`. |
7906
  | `%H` | The hour (24-hour clock) as a decimal number. The modified command `%*N*H` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%OH` interprets the locale's alternative representation. |
7907
  | `%I` | The hour (12-hour clock) as a decimal number. The modified command `%*N*I` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%OI` interprets the locale's alternative representation. |
7908
+ | `%j` | If the type being parsed is a specialization of `duration`, a decimal number of `days`. Otherwise, the day of the year as a decimal number. January 1 is `1`. In either case, the modified command `%*N*j` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 3. Leading zeroes are permitted but not required. |
7909
+ | `%m` | The month as a decimal number. January is `1`. The modified command `%*N*m` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%Om` interprets the locale's alternative representation. |
7910
  | `%M` | The minutes as a decimal number. The modified command `%*N*M` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%OM` interprets the locale's alternative representation. |
7911
  | `%n` | Matches one whitespace character. *`%n`, `%t`, and a space can be combined to match a wide range of whitespace patterns. For example, `"%n "` matches one or more whitespace characters, and `"%n%t%t"` matches one to three whitespace characters.* |
7912
  | `%p` | The locale's equivalent of the AM/PM designations associated with a 12-hour clock. |
7913
  | `%r` | The locale's 12-hour clock time. |
7914
  | `%R` | Equivalent to `%H:%M`. |
7915
  | `%S` | The seconds as a decimal number. The modified command `%*N*S` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2 if the input time has a precision convertible to seconds. Otherwise the default width is determined by the decimal precision of the input and the field is interpreted as a `long double` in a fixed format. If encountered, the locale determines the decimal point character. Leading zeroes are permitted but not required. The modified command `%OS` interprets the locale's alternative representation. |
7916
  | `%t` | Matches zero or one whitespace characters. |
7917
  | `%T` | Equivalent to `%H:%M:%S`. |
7918
+ | `%u` | The calendar day of week as a decimal number (`1`-`7`), as specified in ISO 8601-1:2019, where Monday is `1`. The modified command `%*N*u` specifies the maximum number of characters to read. If `*N*` is not specified, the default is `1`. Leading zeroes are permitted but not required. |
7919
  | `%U` | The week number of the year as a decimal number. The first Sunday of the year is the first day of week `01`. Days of the same year prior to that are in week `00`. The modified command `%*N*U` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%OU` interprets the locale's alternative representation. |
7920
+ | `%V` | The calendar week of year as a decimal number, as specified in ISO 8601-1:2019 for the week calendar. The modified command `%*N*V` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. |
7921
  | `%w` | The weekday as a decimal number (`0`-`6`), where Sunday is `0`. The modified command `%*N*w` specifies the maximum number of characters to read. If `*N*` is not specified, the default is `1`. Leading zeroes are permitted but not required. The modified command `%Ow` interprets the locale's alternative representation. |
7922
  | `%W` | The week number of the year as a decimal number. The first Monday of the year is the first day of week `01`. Days of the same year prior to that are in week `00`. The modified command `%*N*W` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified command `%OW` interprets the locale's alternative representation. |
7923
  | `%x` | The locale's date representation. The modified command `%Ex` interprets the locale's alternate date representation. |
7924
  | `%X` | The locale's time representation. The modified command `%EX` interprets the locale's alternate time representation. |
7925
  | `%y` | The last two decimal digits of the year. If the century is not otherwise specified (e.g., with `%C`), values in the range {[}`69`, `99`{]} are presumed to refer to the years 1969 to 1999, and values in the range {[}`00`, `68`{]} are presumed to refer to the years 2000 to 2068. The modified command `%*N*y` specifies the maximum number of characters to read. If `*N*` is not specified, the default is 2. Leading zeroes are permitted but not required. The modified commands `%Ey` and `%Oy` interpret the locale's alternative representation. |
 
7927
  | `%z` | The offset from UTC in the format `[+|-]hh[mm]`. For example `-0430` refers to 4 hours 30 minutes behind UTC, and `04` refers to 4 hours ahead of UTC. The modified commands `%Ez` and `%Oz` parse a `:` between the hours and minutes and render leading zeroes on the hour field optional: `[+|-]h[h][:mm]`. For example `-04:30` refers to 4 hours 30 minutes behind UTC, and `4` refers to 4 hours ahead of UTC. |
7928
  | `%Z` | The time zone abbreviation or name. A single word is parsed. This word can only contain characters from the basic character set [[lex.charset]] that are alphanumeric, or one of `'_'`, `'/'`, `'-'`, or `'+'`. |
7929
  | `%%` | A `%` character is extracted. |
7930
 
7931
 
7932
+ ## Hash support <a id="time.hash">[[time.hash]]</a>
7933
+
7934
+ ``` cpp
7935
+ template<class Rep, class Period> struct hash<chrono::duration<Rep, Period>>;
7936
+ ```
7937
+
7938
+ The specialization `hash<chrono::duration<Rep, Period>>` is
7939
+ enabled [[unord.hash]] if and only if
7940
+ `hash<Rep>` is enabled. The member functions are not guaranteed to be
7941
+ `noexcept`.
7942
+
7943
+ ``` cpp
7944
+ template<class Clock, class Duration> struct hash<chrono::time_point<Clock, Duration>>;
7945
+ ```
7946
+
7947
+ The specialization `hash<chrono::time_point<Clock, Duration>>` is
7948
+ enabled [[unord.hash]] if and only if `hash<Duration>` is enabled. The
7949
+ member functions are not guaranteed to be `noexcept`.
7950
+
7951
+ ``` cpp
7952
+ template<> struct hash<chrono::day>;
7953
+ template<> struct hash<chrono::month>;
7954
+ template<> struct hash<chrono::year>;
7955
+ template<> struct hash<chrono::weekday>;
7956
+ template<> struct hash<chrono::weekday_indexed>;
7957
+ template<> struct hash<chrono::weekday_last>;
7958
+ template<> struct hash<chrono::month_day>;
7959
+ template<> struct hash<chrono::month_day_last>;
7960
+ template<> struct hash<chrono::month_weekday>;
7961
+ template<> struct hash<chrono::month_weekday_last>;
7962
+ template<> struct hash<chrono::year_month>;
7963
+ template<> struct hash<chrono::year_month_day>;
7964
+ template<> struct hash<chrono::year_month_day_last>;
7965
+ template<> struct hash<chrono::year_month_weekday>;
7966
+ template<> struct hash<chrono::year_month_weekday_last>;
7967
+ ```
7968
+
7969
+ The specializations are enabled [[unord.hash]].
7970
+
7971
+ [*Note 1*: All the `hash<Key>` specializations listed above meet the
7972
+ *Cpp17Hash* requirements, even when called on objects `k` of type `Key`
7973
+ such that `k.ok()` is `false`. — *end note*]
7974
+
7975
+ ``` cpp
7976
+ template<class Duration, class TimeZonePtr>
7977
+ struct hash<chrono::zoned_time<Duration, TimeZonePtr>>;
7978
+ ```
7979
+
7980
+ The specialization `hash<chrono::zoned_time<Duration, TimeZonePtr>>` is
7981
+ enabled [[unord.hash]] if and only if `hash<Duration>` is enabled and
7982
+ `hash<TimeZonePtr>` is enabled. The member functions are not guaranteed
7983
+ to be `noexcept`.
7984
+
7985
+ ``` cpp
7986
+ template<> struct hash<chrono::leap_second>;
7987
+ ```
7988
+
7989
+ The specialization is enabled [[unord.hash]].
7990
+
7991
  ## Header `<ctime>` synopsis <a id="ctime.syn">[[ctime.syn]]</a>
7992
 
7993
  ``` cpp
7994
+ #define __STDC_VERSION_TIME_H__ 202311L
7995
+
7996
  #define NULL see [support.types.nullptr]
7997
  #define CLOCKS_PER_SEC see below
7998
  #define TIME_UTC see below
7999
+ #define TIME_MONOTONIC see below // optional
8000
+ #define TIME_ACTIVE see below // optional
8001
+ #define TIME_THREAD_ACTIVE see below // optional
8002
 
8003
  namespace std {
8004
  using size_t = see [support.types.layout];
8005
  using clock_t = see below;
8006
  using time_t = see below;
 
8009
  struct tm;
8010
 
8011
  clock_t clock();
8012
  double difftime(time_t time1, time_t time0);
8013
  time_t mktime(tm* timeptr);
8014
+ time_t timegm(tm* timeptr);
8015
  time_t time(time_t* timer);
8016
  int timespec_get(timespec* ts, int base);
8017
+ int timespec_getres(timespec* ts, int base);
 
8018
  tm* gmtime(const time_t* timer);
8019
+ tm* gmtime_r(const time_t* timer, tm* buf);
8020
  tm* localtime(const time_t* timer);
8021
+ tm* localtime_r(const time_t* timer, tm* buf);
8022
  size_t strftime(char* s, size_t maxsize, const char* format, const tm* timeptr);
8023
  }
8024
  ```
8025
 
8026
  The contents of the header `<ctime>` are the same as the C standard
8027
  library header `<time.h>`.[^1]
8028
 
8029
+ The functions `gmtime` and `localtime` are not required to avoid data
8030
+ races [[res.on.data.races]].
8031
 
8032
+ See also: ISO C 7.29
8033
 
8034
  <!-- Link reference definitions -->
8035
  [basic.lookup.argdep]: basic.md#basic.lookup.argdep
8036
  [cpp17.equalitycomparable]: #cpp17.equalitycomparable
8037
  [cpp17.lessthancomparable]: #cpp17.lessthancomparable
8038
  [ctime.syn]: #ctime.syn
8039
  [dcl.constexpr]: dcl.md#dcl.constexpr
8040
  [filesystems]: input.md#filesystems
8041
+ [format.formatter]: text.md#format.formatter
8042
+ [format.string]: text.md#format.string
8043
+ [formatter.requirements]: text.md#formatter.requirements
8044
  [intro.multithread]: basic.md#intro.multithread
8045
  [lex.charset]: lex.md#lex.charset
8046
  [meta.rqmts]: meta.md#meta.rqmts
8047
  [numeric.requirements]: numerics.md#numeric.requirements
8048
  [over.ics.rank]: over.md#over.ics.rank
 
8160
  [time.duration.observer]: #time.duration.observer
8161
  [time.duration.special]: #time.duration.special
8162
  [time.format]: #time.format
8163
  [time.format.spec]: #time.format.spec
8164
  [time.general]: #time.general
8165
+ [time.hash]: #time.hash
8166
  [time.hms]: #time.hms
8167
  [time.hms.members]: #time.hms.members
8168
  [time.hms.nonmembers]: #time.hms.nonmembers
8169
  [time.hms.overview]: #time.hms.overview
8170
  [time.hms.width]: #time.hms.width
 
8215
  [time.zone.zonedtime.ctor]: #time.zone.zonedtime.ctor
8216
  [time.zone.zonedtime.members]: #time.zone.zonedtime.members
8217
  [time.zone.zonedtime.nonmembers]: #time.zone.zonedtime.nonmembers
8218
  [time.zone.zonedtime.overview]: #time.zone.zonedtime.overview
8219
  [time.zone.zonedtraits]: #time.zone.zonedtraits
8220
+ [unord.hash]: utilities.md#unord.hash
8221
 
8222
  [^1]: `strftime` supports the C conversion specifiers `C`, `D`, `e`,
8223
  `F`, `g`, `G`, `h`, `r`, `R`, `t`, `T`, `u`, `V`, and `z`, and the
8224
  modifiers `E` and `O`.