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function is not described

wp_checkdate() WP 3.5.0

Test if the supplied date is valid for the Gregorian calendar.

Hooks in function
Return

true/false. True if valid date, false if not valid date.

Usage

wp_checkdate( $month, $day, $year, $source_date );
$month(int) (required)
Month number.
$day(int) (required)
Day number.
$year(int) (required)
Year number.
$source_date(string) (required)
The date to filter.

Code of wp checkdate: wp-includes/functions.php WP 5.2.2

<?php
function wp_checkdate( $month, $day, $year, $source_date ) {
	/**
	 * Filters whether the given date is valid for the Gregorian calendar.
	 *
	 * @since 3.5.0
	 *
	 * @param bool   $checkdate   Whether the given date is valid.
	 * @param string $source_date Date to check.
	 */
	return apply_filters( 'wp_checkdate', checkdate( $month, $day, $year ), $source_date );
}