title: Angular Date pipe adds plus dot after year component
body: <p>I'm using Angular version 2.4.5.</p>
  
  <p>If I use the date pipe without any format it creates double dots after the year. If I use the pipe with the format: 'yyyyMM.dd.' it gives the correct date format</p>
  
  <ul>
  <li><code>{{startDate | date}}</code> => 2017..07.07.</li>
  <li><code>{{startDate | date: 'yyyyMM.dd.'}}</code> => 2017.07.07.</li>
  </ul>
  
  <p>Which means that I can not set this as the value of a date input because it waits for the format <code>yyyy-MM-dd</code> and yyyy always have a plus dot that causes an error on input element. Neither of these work:</p>
  
  <pre><code>&lt;input type="date" class="form-control" id="startDate" [ngModel]="currentItem.startDate | date: 'y-MM-dd'"
  (ngModelChange)="currentItem.startDate = $event" name="startdate"&gt;
  </code></pre>
  
  <p></p>
  
  <p>How can I solve this without using a new model with a correctly converted date string?</p>
  
  <p><strong>Update 2017-07-12</strong>:
  currentItem.startDate is a Date() object eg:</p>
  
  <pre><code>let currentItem.startDate = new Date();
  </code></pre>
  
  <p>The locale I'm trying to use is 'hu-HU' but the two dots were present without any locale provider. In that case the date pipe without any format strings gave the correct format for the input. (yyyy-MM-dd)</p>
  
  <pre><code>{{currentItem.startDate | date}}
  </code></pre>