diff --git a/source/Ox/js/Format.js b/source/Ox/js/Format.js
index 212586bd..dfbe46f5 100644
--- a/source/Ox/js/Format.js
+++ b/source/Ox/js/Format.js
@@ -422,13 +422,13 @@ Ox.formatDateRangeDuration <f> Formats the duration of a date range as a string
 Ox.formatDateRangeDuration = function(start, end, utc) {
     end = end || Ox.formatDate(new Date(), '%Y-%m-%d');
     var date = Ox.parseDate(start, utc),
-        dates = [start, end].map(function(str) {
-            return Ox.parseDate(str, utc);
+        dates = [start, end].map(function(string) {
+            return Ox.parseDate(string, utc);
         }),
         keys = ['year', 'month', 'day', 'hour', 'minute', 'second'],
         parts = ['FullYear', 'Month', 'Date', 'Hours', 'Minutes', 'Seconds'],
         values = [];
-    keys.forEach(function(key, i) {
+    date && keys.forEach(function(key, i) {
         while (true) {
             if (key == 'month') {
                 // set the day to the same day in the next month,