Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 11300)
+++ wp-includes/functions.php	(working copy)
@@ -3087,9 +3087,9 @@
 		&& function_exists('timezone_open')
 		&& function_exists('timezone_offset_get')
 		)
-		return true;
+		return apply_filters('timezone_support',true);
 
-	return false;
+	return apply_filters('timezone_support',false);
 }
 
 /**