[time.clock.utc.nonmembers]

# 30 Time library [[time]](./#time)

## 30.7 Clocks [[time.clock]](time.clock#utc.nonmembers)

### 30.7.3 Class utc_clock [[time.clock.utc]](time.clock.utc#nonmembers)

#### 30.7.3.3 Non-member functions [time.clock.utc.nonmembers]

[ð](#lib:operator%3c%3c,utc_time)

`template<class charT, class traits, class Duration>
  basic_ostream<charT, traits>&
    operator<<(basic_ostream<charT, traits>& os, const utc_time<Duration>& t);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/time.tex#L2937)

*Effects*: Equivalent to:return os << format(os.getloc(), *STATICALLY-WIDEN*<charT>("{:L%F %T}"), t);

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/time.tex#L2944)

[*Example [1](#example-1)*: 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

```

â *end example*]

[ð](#lib:from_stream,utc_time)

`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);
`

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/time.tex#L2977)

*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]](time.parse "30.13 Parsing")[.](#3.sentence-1)

If the parse fails to decode a valid date,is.setstate(ios_base​::​failbit) is called andtp is not modified[.](#3.sentence-2)

If %Z is used and successfully parsed,
that value will be assigned to *abbrev if abbrev is non-null[.](#3.sentence-3)

If %z (or a modified variant) is used and successfully parsed,
that value will be assigned to *offset if offset is non-null[.](#3.sentence-4)

Additionally, the parsed offset will be subtracted from
the successfully parsed timestamp
prior to assigning that difference to tp[.](#3.sentence-5)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/time.tex#L2994)

*Returns*: is[.](#4.sentence-1)

[ð](#lib:leap_second_info)

`struct leap_second_info {
  bool    is_leap_second;
  seconds elapsed;
};
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/time.tex#L3008)

The type leap_second_info has data members and special members specified above[.](#5.sentence-1)

It has no base classes or members other than those specified[.](#5.sentence-2)

[ð](#lib:get_leap_second_info)

`template<class Duration>
  leap_second_info get_leap_second_info(const utc_time<Duration>& ut);
`

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/time.tex#L3021)

*Returns*: A leap_second_info lsi,
where lsi.is_leap_second is true if ut is during a positive leap second insertion, and
otherwise false[.](#6.sentence-1)

lsi.elapsed is the sum of leap seconds between 1970-01-01 and ut[.](#6.sentence-2)

If lsi.is_leap_second is true,
the leap second referred to by ut is included in the sum[.](#6.sentence-3)
