namespace std::chrono { class year { short y_; // exposition only public: year() = default; explicit constexpr year(int y) noexcept; constexpr year& operator++() noexcept; constexpr year operator++(int) noexcept; constexpr year& operator--() noexcept; constexpr year operator--(int) noexcept; constexpr year& operator+=(const years& y) noexcept; constexpr year& operator-=(const years& y) noexcept; constexpr year operator+() const noexcept; constexpr year operator-() const noexcept; constexpr bool is_leap() const noexcept; explicit constexpr operator int() const noexcept; constexpr bool ok() const noexcept; static constexpr year min() noexcept; static constexpr year max() noexcept; }; }