wp_resolve_post_date() WordPress Function

function wp_resolve_post_date( $post_date = '', $post_date_gmt = '' ) {
	// If the date is empty, set the date to now.
	if ( empty( $post_date ) || '0000-00-00 00:00:00' === $post_date ) {
		if ( empty( $post_date_gmt ) || '0000-00-00 00:00:00' === $post_date_gmt ) {
			$post_date = current_time( 'mysql' );
		} else {
			$post_date = get_date_from_gmt( $post_date_gmt );
		}
	}

	// Validate the date.
	$month = substr( $post_date, 5, 2 );
	$day   = substr( $post_date, 8, 2 );
	$year  = substr( $post_date, 0, 4 );

	$valid_date = wp_checkdate( $month, $day, $year, $post_date );

	if ( ! $valid_date ) {
		return false;
	}
	return $post_date;
}