std::chrono::day - cppreference.com

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C-style date and time

The class day represents a day in a month. Its normal range is [1, 31], but it may hold any number in [0, 255].

(constructor)	constructs a `day` (public member function) [edit]
operator++operator++(int)operator--operator--(int)	increments or decrements the day (public member function) [edit]
operator+=operator-=	adds or subtracts a number of days (public member function) [edit]
operator unsigned	retrieves the stored day value (public member function) [edit]
ok	checks if the stored day value is in the normal range (public member function) [edit]

operator==operator<=> (C++20)	compares two `day` values (function) [edit]
operator+operator- (C++20)	adds or subtracts a number of days and a `day`, or find the difference between two `day`s (function) [edit]
operator<< (C++20)	outputs a `day` into a stream (function template) [edit]
from_stream (C++20)	parses a `day` from a stream according to the provided format (function template) [edit]

std::formatter<std::chrono::day> (C++20)	formatting support for `day` (class template specialization) [edit]
std::hash<std::chrono::day> (C++26)	hash support for `std::chrono::day` (class template specialization)

Defined in inline namespace `std::literals::chrono_literals`
operator""d (C++20)	a std::chrono::day literal representing a day of a month (function) [edit]