namespace std::chrono { class weekday { unsigned char wd_; // exposition only public: weekday() = default; 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; }; }

weekday represents a day of the week in the civil calendar.

It normally holds values in the range 0 to 6,
corresponding to Sunday through Saturday, but
it may hold non-negative values outside this range.

It can be constructed with any unsigned value,
which will be subsequently truncated to fit into weekday's unspecified internal storage.