Index: wp-includes/functions-formatting.php
===================================================================
--- wp-includes/functions-formatting.php	(revision 3835)
+++ wp-includes/functions-formatting.php	(working copy)
@@ -521,6 +521,7 @@
 
 
 function backslashit($string) {
+	$string = preg_replace('/([0-9])/', '\\\\\\\\\1', $string);
 	$string = preg_replace('/([a-z])/i', '\\\\\1', $string);
 	return $string;
 }
Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 3835)
+++ wp-includes/functions.php	(working copy)
@@ -32,10 +32,10 @@
 		$dateweekday = $weekday[date('w', $i)];
 		$dateweekday_abbrev = $weekday_abbrev[$dateweekday];
 		$dateformatstring = ' '.$dateformatstring;
-		$dateformatstring = preg_replace("/([^\\\])D/", "\${1}".backslashit($dateweekday_abbrev), $dateformatstring);
-		$dateformatstring = preg_replace("/([^\\\])F/", "\${1}".backslashit($datemonth), $dateformatstring);
-		$dateformatstring = preg_replace("/([^\\\])l/", "\${1}".backslashit($dateweekday), $dateformatstring);
-		$dateformatstring = preg_replace("/([^\\\])M/", "\${1}".backslashit($datemonth_abbrev), $dateformatstring);
+		$dateformatstring = preg_replace("/([^\\\])D/", "\\1".backslashit($dateweekday_abbrev), $dateformatstring);
+		$dateformatstring = preg_replace("/([^\\\])F/", "\\1".backslashit($datemonth), $dateformatstring);
+		$dateformatstring = preg_replace("/([^\\\])l/", "\\1".backslashit($dateweekday), $dateformatstring);
+		$dateformatstring = preg_replace("/([^\\\])M/", "\\1".backslashit($datemonth_abbrev), $dateformatstring);
 
 		$dateformatstring = substr($dateformatstring, 1, strlen($dateformatstring)-1);
 	}