--- date_api.module	2009-05-12 12:57:45.000000000 +0000
+++ date_api.module	2009-06-17 16:32:56.000000000 +0000
@@ -673,6 +673,10 @@ function date_format_date($date, $type =
     switch ($c) {
       // Use date_t() for ambiguous short strings that need translation.
       // We send long day and month names to date_t(), along with context.
+      case 'c':
+        // The ISO date format does not need translation
+        $datestring .= date_format($date, $c);
+        break;
       case 'l':
         $datestring .= date_t(date_format($date, 'l'), 'day_name', $langcode);
         break;