25 Time library [time]

25.7 Clocks [time.clock]

25.7.3 Class tai_­clock [time.clock.tai]

25.7.3.3 Non-member functions [time.clock.tai.nonmembers]

template<class charT, class traits, class Duration> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const tai_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 tai_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 "TAI".
If %z is used (or a modified variant of %z), an offset of 0min will be formatted.
The date and time formatted shall be equivalent to that formatted by a sys_­time initialized with:
sys_time<Duration>{tp.time_since_epoch()} -
  (sys_days{1970y/January/1} - sys_days{1958y/January/1})
Returns: os.
[Example
:
auto st = sys_days{2000y/January/1};
auto tt = clock_cast<tai_clock>(st);
cout << format("%F %T %Z == ", st) << format("%F %T %Z\n", tt);
Produces this output:
2000-01-01 00:00:00 UTC == 2000-01-01 00:00:32 TAI
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, tai_time<Duration>& tp, basic_string<charT, traits, Alloc>* abbrev = nullptr, minutes* offset = nullptr);
Effects: Attempts to parse the input stream is into the tai_­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.