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

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';
}

2020
-0016
-32768 is not a valid year

See also