Utilities library
General utilities
Date and time
Function objects
Formatting library (C++20)
Relational operators (deprecated in C++20)
Integer comparison functions
Swap and type operations
Common vocabulary types
Elementary string conversions
Defined in header <chrono>
template< class CharT, class Traits >

std::basic_ostream<CharT, Traits>&
operator<<( std::basic_ostream<CharT, Traits>& os,

            const std::chrono::year_month_day& ymd );
(since C++20)

Outputs a textual representation of ymd into the stream os. This first forms a std::basic_string<CharT> s consisting of a textual representation of the date in the format yyyy-mm-dd (same as the one output by formatter with the %F specifier). Then, if !ymd.ok(), appends " is not a valid date" to s. Inserts s into os.

Equivalent to

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

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

[edit] Return value


[edit] See also

stores formatted representation of the arguments in a new string
(function template) [edit]
specialization of std::formatter that formats a year_month_day according to the provided format
(class template specialization) [edit]