25 Time library [time]

25.7 Clocks [time.clock]

25.7.2 Class utc_­clock [time.clock.utc]

25.7.2.3 Non-member functions [time.clock.utc.nonmembers]

template<class charT, class traits, class Duration> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const utc_time<Duration>& t);
Effects: Calls to_­stream(os, fmt, t), where fmt is a string containing "%F %T" widened to charT.
Returns: os.
template<class charT, class traits, class Duration> basic_ostream<charT, traits>& to_stream(basic_ostream<charT, traits>& os, const charT* fmt, const utc_time<Duration>& tp);
Effects: Streams tp into os using the format specified by the NTCTS fmt.
fmt encoding follows the rules specified in [time.format].
If %Z is used, it will be replaced with "UTC" widened to charT.
If %z is used (or a modified variant of %z), an offset of 0min will be formatted.
If tp represents a time during a leap second insertion, and if a seconds field is formatted, the integral portion of that format shall be "60" widened to charT.
Returns: os.
[Example
:
auto t = sys_days{July/1/2015} - 500ms;
auto u = clock_cast<utc_clock>(t);
for (auto i = 0; i < 8; ++i, u += 250ms)
  cout << u << " UTC\n";
Produces this output:
2015-06-30 23:59:59.500 UTC
2015-06-30 23:59:59.750 UTC
2015-06-30 23:59:60.000 UTC
2015-06-30 23:59:60.250 UTC
2015-06-30 23:59:60.500 UTC
2015-06-30 23:59:60.750 UTC
2015-07-01 00:00:00.000 UTC
2015-07-01 00:00:00.250 UTC
end example
]
template<class charT, class traits, class Duration, class Alloc = allocator<charT>> basic_istream<charT, traits>& from_stream(basic_istream<charT, traits>& is, const charT* fmt, utc_time<Duration>& tp, basic_string<charT, traits, Alloc>* abbrev = nullptr, minutes* offset = nullptr);
Effects: Attempts to parse the input stream is into the utc_­time tp using the format flags given in the NTCTS fmt as specified in [time.parse].
If the parse fails to decode a valid date, is.setstate(ios_­base::failbit) shall be called and tp shall not be modified.
If %Z is used and successfully parsed, that value will be assigned to *abbrev if abbrev is non-null.
If %z (or a modified variant) is used and successfully parsed, that value will be assigned to *offset if offset is non-null.
Additionally, the parsed offset will be subtracted from the successfully parsed timestamp prior to assigning that difference to tp.
Returns: is.