27 Time library [time]

27.9 Class template hh_­mm_­ss [time.hms]

27.9.1 Overview [time.hms.overview]

namespace std::chrono {
  template<class Duration> class hh_mm_ss {
    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;

    bool            is_neg;     // exposition only
    chrono::hours   h;          // exposition only
    chrono::minutes m;          // exposition only
    chrono::seconds s;          // exposition only
    precision       ss;         // exposition only
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.
The Duration template parameter dictates the precision to which the time is split.
A hh_­mm_­ss models negative durations with a distinct is_­negative getter that returns true when the input duration is negative.
The individual duration fields always return non-negative durations even when is_­negative() indicates the structure is representing a negative duration.
If Duration is not an instance of duration, the program is ill-formed.