std::chrono::operator<<(std::chrono::year)

< cpp‎ | chrono‎ | year
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

os.

Example

#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:

2020
-0016
-32768 is not a valid year

See also

(C++20)
 stores formatted representation of the arguments in a new string
(function template)
(C++20)
 formatting support for year
(class template specialization)