29 Time library [time]

29.5 Class template duration [time.duration]

29.5.7 Comparisons [time.duration.comparisons]

In the function descriptions that follow, CT represents common_type_t<A, B>, where A and B are the types of the two arguments to the function.
template<class Rep1, class Period1, class Rep2, class Period2> constexpr bool operator==(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
Returns: CT(lhs).count() == CT(rhs).count().
template<class Rep1, class Period1, class Rep2, class Period2> constexpr bool operator<(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
Returns: CT(lhs).count() < CT(rhs).count().
template<class Rep1, class Period1, class Rep2, class Period2> constexpr bool operator>(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
Returns: rhs < lhs.
template<class Rep1, class Period1, class Rep2, class Period2> constexpr bool operator<=(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
Returns: !(rhs < lhs).
template<class Rep1, class Period1, class Rep2, class Period2> constexpr bool operator>=(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
Returns: !(lhs < rhs).
template<class Rep1, class Period1, class Rep2, class Period2> requires three_way_comparable<typename CT::rep> constexpr auto operator<=>(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);
Returns: CT(lhs).count() <=> CT(rhs).count().