fixed conversion from date-String to Number

lib/util.js

@@ -392,8 +392,11 @@ exports.convert = function (object, type) {
 
     case 'number':
     case 'Number':
-      return Number(object.valueOf());
-
+      if (!isNaN(Date.parse(object))) {
+        return moment(object).valueOf();
+      } else {
+        return Number(object.valueOf());
+      }
     case 'string':
     case 'String':
       return String(object);
@@ -1477,4 +1480,4 @@ exports.getScrollBarWidth = function () {
   document.body.removeChild (outer);
 
   return (w1 - w2);
-};
+};