constexpr common_type_t<duration> operator+() const;
constexpr common_type_t<duration> operator-() const;
constexpr duration& operator++();
constexpr duration operator++(int);
constexpr duration& operator--();
constexpr duration operator--(int);
constexpr duration& operator+=(const duration& d);
constexpr duration& operator-=(const duration& d);
constexpr duration& operator*=(const rep& rhs);
constexpr duration& operator/=(const rep& rhs);
constexpr duration& operator%=(const rep& rhs);
constexpr duration& operator%=(const duration& rhs);