27 Time library [time]

27.4 Time-related traits [time.traits]

27.4.2 duration_­values [time.traits.duration.values]

template<class Rep> struct duration_values { public: static constexpr Rep zero() noexcept; static constexpr Rep min() noexcept; static constexpr Rep max() noexcept; };
The duration template uses the duration_­values trait to construct special values of the duration's representation (Rep).
This is done because the representation might be a class type with behavior which requires some other implementation to return these special values.
In that case, the author of that class type should specialize duration_­values to return the indicated values.
static constexpr Rep zero() noexcept;
Returns: Rep(0).
[Note
:
Rep(0) is specified instead of Rep() because Rep() may have some other meaning, such as an uninitialized value.
end note
]
Remarks: The value returned shall be the additive identity.
static constexpr Rep min() noexcept;
Returns: numeric_­limits<Rep>::lowest().
Remarks: The value returned shall compare less than or equal to zero().
static constexpr Rep max() noexcept;
Returns: numeric_­limits<Rep>::max().
Remarks: The value returned shall compare greater than zero().