constexpr year_month_day_last(const chrono::year& y,
const chrono::month_day_last& mdl) noexcept;
constexpr year_month_day_last& operator+=(const months& m) noexcept;
constexpr year_month_day_last& operator-=(const months& m) noexcept;
constexpr year_month_day_last& operator+=(const years& y) noexcept;
constexpr year_month_day_last& operator-=(const years& y) noexcept;
constexpr chrono::year year() const noexcept;
constexpr chrono::month month() const noexcept;
constexpr chrono::month_day_last month_day_last() const noexcept;
constexpr chrono::day day() const noexcept;
constexpr operator sys_days() const noexcept;
constexpr explicit operator local_days() const noexcept;
constexpr bool ok() const noexcept;