title: OrderBy Filter for Zulu time not working as expected
body: <p>I am trying to filter the time <code>latest</code> to <code>null</code> in the below <code>HTML</code>. The time format is in Zulu(UTC) format i.e. <code>'2017/04/01T00:00:00.000Z'</code>. </p>
  
  <pre><code>&lt;li ng-repeat="contact in $ctrl.contacts | orderBy: 'LastChatTime' | filter : searchContact track by $index"&gt;
  </code></pre>
  
  <p>When I do this. In records where time exists are sorted in reverse order and then null records are coming. 
  e.g.: </p>
  
  <pre><code> 1. '2017/03/31T13:00:00.000Z'  
   2. '2017/04/01T00:00:00.000Z'  
   3. `Null`
  </code></pre>
  
  <p>Instead of :</p>
  
  <pre><code> 1. '2017/04/01T00:00:00.000Z' 
   2. '2017/03/31T13:00:00.000Z' 
   3. `Null`
  </code></pre>