27 Time library [time]

27.7 Clocks [time.clock]

27.7.2 Class system_­clock [time.clock.system]

27.7.2.3 Non-member functions [time.clock.system.nonmembers]

template<class charT, class traits, class Duration> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const sys_time<Duration>& tp);
Constraints: treat_­as_­floating_­point_­v<typename Duration​::​rep> is false, and Duration{1} < days{1} is true.
Effects: Equivalent to: return os << format(os.getloc(), STATICALLY-WIDEN("{:L%F %T}"), tp);
[Example 1: cout << sys_seconds{0s} << '\n'; // 1970-01-01 00:00:00 cout << sys_seconds{946'684'800s} << '\n'; // 2000-01-01 00:00:00 cout << sys_seconds{946'688'523s} << '\n'; // 2000-01-01 01:02:03 — end example]
template<class charT, class traits> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const sys_days& dp);
Effects: os << year_­month_­day{dp}.
Returns: os.
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, sys_time<Duration>& tp, basic_string<charT, traits, Alloc>* abbrev = nullptr, minutes* offset = nullptr);
Effects: Attempts to parse the input stream is into the sys_­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) is called and tp is not 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.