29 Time library [time]

29.8 The civil calendar [time.cal]

29.8.4 Class month [time.cal.month]

29.8.4.2 Member functions [time.cal.month.members]

constexpr explicit month(unsigned m) noexcept;
Effects: Initializes m_­ with m.
The value held is unspecified if m is not in the range [0, 255].
constexpr month& operator++() noexcept;
Effects: *this += months{1}.
Returns: *this.
constexpr month operator++(int) noexcept;
Effects: ++(*this).
Returns: A copy of *this as it existed on entry to this member function.
constexpr month& operator--() noexcept;
Effects: *this -= months{1}.
Returns: *this.
constexpr month operator--(int) noexcept;
Effects: --(*this).
Returns: A copy of *this as it existed on entry to this member function.
constexpr month& operator+=(const months& m) noexcept;
Effects: *this = *this + m.
Returns: *this.
constexpr month& operator-=(const months& m) noexcept;
Effects: *this = *this - m.
Returns: *this.
constexpr explicit operator unsigned() const noexcept;
Returns: m_­.
constexpr bool ok() const noexcept;
Returns: 1 <= m_­ && m_­ <= 12.