constexpr explicit weekday(unsigned wd) noexcept;
constexpr weekday(const sys_days& dp) noexcept;
constexpr explicit weekday(const local_days& dp) noexcept;
constexpr weekday& operator++() noexcept;
constexpr weekday operator++(int) noexcept;
constexpr weekday& operator--() noexcept;
constexpr weekday operator--(int) noexcept;
constexpr weekday& operator+=(const days& d) noexcept;
constexpr weekday& operator-=(const days& d) noexcept;
constexpr unsigned c_encoding() const noexcept;
constexpr unsigned iso_encoding() const noexcept;
constexpr bool ok() const noexcept;
constexpr weekday_indexed operator[](unsigned index) const noexcept;
constexpr weekday_last operator[](last_spec) const noexcept;