Ticket #42394: 42394.4.diff

src/wp-includes/customize/class-wp-customize-date-time-control.php

@@ -100 +100 @@
                 $timezone_info = $this->get_timezone_info();
 
                 $date_format = get_option( 'date_format' );
-                foreach ( array( 'Y', 'y', 'o' ) as $year_token ) {
-                        $date_format = preg_replace( '/(?<!\\\\)' . $year_token . '/', '%1$s', $date_format );
-                }
-                foreach ( array( 'F', 'm', 'M', 'n' ) as $month_token ) {
-                        $date_format = preg_replace( '/(?<!\\\\)' . $month_token . '/', '%2$s', $date_format );
-                }
-                foreach ( array( 'j', 'd' ) as $day_token ) {
-                        $date_format = preg_replace( '/(?<!\\\\)' . $day_token . '/', '%3$s', $date_format );
+                $date_format = preg_replace( '/(?<!\\\\)[Yyo]/', '%1$s', $date_format );
+                $date_format = preg_replace( '/(?<!\\\\)[FmMn]/', '%2$s', $date_format );
+                $date_format = preg_replace( '/(?<!\\\\)[jd]/', '%3$s', $date_format );
+
+                // Fallback to ISO date format if year, month, or day are missing from the date format.
+                if ( 1 !== substr_count( $date_format, '%1$s' ) || 1 !== substr_count( $date_format, '%2$s' ) || 1 !== substr_count( $date_format, '%3$s' ) ) {
+                        $date_format = '%1$s-%2$s-%3$s';
                 }
                 ?>