diff --git a/html/sites/all/modules/duration/duration.inc b/html/sites/all/modules/duration/duration.inc
index 10118cd..97bb6bb 100644
--- a/html/sites/all/modules/duration/duration.inc
+++ b/html/sites/all/modules/duration/duration.inc
@@ -561,7 +561,7 @@ class Duration {
   function add_to_date($date) {
     $modifier = '';
     foreach ($this->duration as $metric => $value) {
-      $modifier = $value . ' ' . $metric;
+      $modifier .= $value . ' ' . $metric;
     }
     if (empty($modifier)) {
       return; // nothing to change