Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 2507)
+++ wp-includes/functions.php	(working copy)
@@ -59,16 +59,18 @@
 }
 
 function date_i18n($dateformatstring, $unixtimestamp) {
-	global $month, $weekday;
+	global $month, $weekday, $month_abbrev, $weekday_abbrev;
 	$i = $unixtimestamp; 
 	if ((!empty($month)) && (!empty($weekday))) {
 		$datemonth = $month[date('m', $i)];
+		$datemonth_abbrev = $month_abbrev[$datemonth];
 		$dateweekday = $weekday[date('w', $i)];
+		$dateweekday_abbrev = $weekday_abbrev[$dateweekday]; 		
 		$dateformatstring = ' '.$dateformatstring;
-		$dateformatstring = preg_replace("/([^\\\])D/", "\\1".backslashit(substr($dateweekday, 0, 3)), $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(substr($datemonth, 0, 3)), $dateformatstring);
+		$dateformatstring = preg_replace("/([^\\\])M/", "\\1".backslashit($datemonth_abbrev), $dateformatstring);
 		$dateformatstring = substr($dateformatstring, 1, strlen($dateformatstring)-1);
 	}
 	$j = @date($dateformatstring, $i);