diff --git a/app/webroot/css.php b/app/webroot/css.php
index 52b57fee7..969dd0e27 100644
--- a/app/webroot/css.php
+++ b/app/webroot/css.php
@@ -95,7 +95,7 @@ if (!class_exists('File')) {
 
 	header("Date: " . date("D, j M Y G:i:s ", $templateModified) . 'GMT');
 	header("Content-Type: text/css");
-	header("Expires: " . gmdate("D, j M Y H:i:s", time() + DAY) . " GMT");
+	header("Expires: " . gmdate("D, d M Y H:i:s", time() + DAY) . " GMT");
 	header("Cache-Control: max-age=86400, must-revalidate"); // HTTP/1.1
 	header("Pragma: cache");        // HTTP/1.0
 	print $output;