[time.cal.md.overview]

# 30 Time library [[time]](./#time)

## 30.8 The civil calendar [[time.cal]](time.cal#md.overview)

### 30.8.9 Class month_day [[time.cal.md]](time.cal.md#overview)

#### 30.8.9.1 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; };}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/time.tex#L5512)

month_day represents a specific day of a specific month,
but with an unspecified year[.](#1.sentence-1)

month_day meets the [*Cpp17EqualityComparable*](utility.arg.requirements#:Cpp17EqualityComparable "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [28](utility.arg.requirements#tab:cpp17.equalitycomparable "Table 28: Cpp17EqualityComparable requirements"))
and [*Cpp17LessThanComparable*](utility.arg.requirements#:Cpp17LessThanComparable "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [29](utility.arg.requirements#tab:cpp17.lessthancomparable "Table 29: Cpp17LessThanComparable requirements")) requirements[.](#1.sentence-2)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/time.tex#L5518)

month_day is a trivially copyable and standard-layout class type[.](#2.sentence-1)
