[time.hms.overview]

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

## 30.9 Class template hh_mm_ss [[time.hms]](time.hms#overview)

### 30.9.1 Overview [time.hms.overview]

namespace std::chrono {template<class Duration> class hh_mm_ss {public:static constexpr unsigned fractional_width = *see below*; using precision = *see below*; constexpr hh_mm_ss() noexcept : hh_mm_ss{Duration::zero()} {}constexpr explicit hh_mm_ss(Duration d); constexpr bool is_negative() const noexcept; constexpr chrono::hours hours() const noexcept; constexpr chrono::minutes minutes() const noexcept; constexpr chrono::seconds seconds() const noexcept; constexpr precision subseconds() const noexcept; constexpr explicit operator precision() const noexcept; constexpr precision to_duration() const noexcept; private:bool is_neg; // *exposition only* chrono::hours h; // *exposition only* chrono::minutes m; // *exposition only* chrono::seconds s; // *exposition only* precision ss; // *exposition only*};}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/time.tex#L8423)

The hh_mm_ss class template
splits a duration into a multi-field time structure*hours*:*minutes*:*seconds* and
possibly *subseconds*,
where *subseconds* will be a duration unit
based on a non-positive power of 10[.](#1.sentence-1)

The Duration template parameter dictates the precision
to which the time is split[.](#1.sentence-2)

A hh_mm_ss models negative durations
with a distinct is_negative getter
that returns true when the input duration is negative[.](#1.sentence-3)

The individual duration fields always return non-negative durations
even when is_negative() indicates
the structure is representing a negative duration[.](#1.sentence-4)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/time.tex#L8440)

If Duration is not a specialization of duration,
the program is ill-formed[.](#2.sentence-1)