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& y );
(since C++20)

Forms a std::basic_string<CharT> s consisting of the year value stored in y formatted as a decimal number, left-padded with ​0​ to four digits if the result would otherwise be less than four digits. Then, if !y.ok(), append " is not a valid year" to the formatted string. Inserts that string into os.

Equivalent to.

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

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

Return value



#include <chrono>
#include <iostream>
int main()
    constexpr std::chrono::year y1{2020}, y2{-020}, y3{98304};
    std::cout << y1 << '\n'
              << y2 << '\n'
              << y3 << '\n';

Possible output:

-32768 is not a valid year

See also

stores formatted representation of the arguments in a new string
(function template)
formatting support for year
(class template specialization)

© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.