29 Time library [time]

29.8 The civil calendar [time.cal]

29.8.7 Class weekday_indexed [time.cal.wdidx] Overview [time.cal.wdidx.overview]

namespace std::chrono { class weekday_indexed { chrono::weekday wd_; // exposition only unsigned char index_; // exposition only public: weekday_indexed() = default; constexpr weekday_indexed(const chrono::weekday& wd, unsigned index) noexcept; constexpr chrono::weekday weekday() const noexcept; constexpr unsigned index() const noexcept; constexpr bool ok() const noexcept; }; }
weekday_indexed represents a weekday and a small index in the range 1 to 5.
This class is used to represent the first, second, third, fourth, or fifth weekday of a month.
[Note 1: 
A weekday_indexed object can be constructed by indexing a weekday with an unsigned.
— end note]
[Example 1: constexpr auto wdi = Sunday[2]; // wdi is the second Sunday of an as yet unspecified month static_assert(wdi.weekday() == Sunday); static_assert(wdi.index() == 2); — end example]
weekday_indexed is a trivially copyable and standard-layout class type.