Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 17776)
+++ wp-includes/functions.php	(working copy)
@@ -83,7 +83,7 @@
  */
 function date_i18n( $dateformatstring, $unixtimestamp = false, $gmt = false ) {
 	global $wp_locale;
-	$i = $unixtimestamp;
+	$i = $unixtimestamp ? $unixtimestamp : current_time( 'timestamp', $gmt );
 
 	// store original value for language with untypical grammars
 	// see http://core.trac.wordpress.org/ticket/9396