26 Time library [time]

26.8 The civil calendar [time.cal]

26.8.7 Class weekday_­indexed [time.cal.wdidx]

26.8.7.3 Non-member functions [time.cal.wdidx.nonmembers]

constexpr bool operator==(const weekday_indexed& x, const weekday_indexed& y) noexcept;
Returns: x.weekday() == y.weekday() && x.index() == y.index().
template<class charT, class traits> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const weekday_indexed& wdi);
Effects: os << wdi.weekday() << '[' << wdi.index().
If wdi.index() is in the range [1, 5], appends with ']', otherwise appends with " is not a valid index]".
Returns: os.