27 Time library [time]

27.8 The civil calendar [time.cal]

27.8.11 Class month_­weekday [time.cal.mwd] Overview [time.cal.mwd.overview]

namespace std::chrono {
  class month_weekday {
    chrono::month           m_;         // exposition only
    chrono::weekday_indexed wdi_;       // exposition only
    constexpr month_weekday(const chrono::month& m, const chrono::weekday_indexed& wdi) noexcept;

    constexpr chrono::month           month()           const noexcept;
    constexpr chrono::weekday_indexed weekday_indexed() const noexcept;
    constexpr bool ok() const noexcept;
month_­weekday represents the weekday of a month, of an as yet unspecified year.
To do this the month_­weekday stores a month and a weekday_­indexed.
constexpr auto mwd
    = February/Tuesday[3];              // mwd is the third Tuesday of February of an as yet unspecified year
static_assert(mwd.month() == February);
static_assert(mwd.weekday_indexed() == Tuesday[3]);
— end example
month_­weekday is a trivially copyable and standard-layout class type.