29 Time library [time]

29.8 The civil calendar [time.cal]

29.8.9 Class month_day [time.cal.md] Overview [time.cal.md.overview]

namespace std::chrono { class month_day { chrono::month m_; // exposition only chrono::day d_; // exposition only public: month_day() = default; constexpr month_day(const chrono::month& m, const chrono::day& d) noexcept; constexpr chrono::month month() const noexcept; constexpr chrono::day day() const noexcept; constexpr bool ok() const noexcept; }; }
month_day represents a specific day of a specific month, but with an unspecified year.
month_day meets the Cpp17EqualityComparable (Table 28) and Cpp17LessThanComparable (Table 29) requirements.
month_day is a trivially copyable and standard-layout class type.