std::chrono::operator<<(std::chrono::day)

template< class CharT, class Traits >
std::basic_ostream<CharT, Traits>&
operator<<( std::basic_ostream<CharT, Traits>& os, const std::chrono::day& d );

Forms a std::basic_string<CharT> s consisting of the day value stored in d formatted as a decimal number, with a leading zero if the result would otherwise be a single decimal digit. Then, if !d.ok(), append " is not a valid day" to the formatted string. Inserts that string into os.

Equivalent to.

return os << (d.ok() ?
std::format(STATICALLY_WIDEN<CharT>("{:%d}"), d) :
std::format(STATICALLY_WIDEN<CharT>("{:%d} is not a valid day"), d));

where STATICALLY_WIDEN<CharT>("...") is "..." if CharT is char, and L"..." if CharT is wchar_t.

Return value

os.

See also