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

From cppreference.com
< cpp‎ | chrono‎ | day

template <class CharT, class Traits> std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os, const std::chrono::day& d); |  | (since C++20)

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. Inserts that string into `os`. Then, if !d.ok(), inserts the string " is not a valid day" into `os`.

### Return value

`os`.

### Notes

This `operator<<` is primarily intended for debugging use. For control over formatting, use std::chrono::format.

### See also

format (C++20) | formats a streamable `chrono` object for insertion (function template)
to_stream | outputs a `day` into a stream according to the provided format (function template)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/chrono/day/operator_ltlt&oldid=104657"