title: Bootstrap Month Picker not work correctly
body: <p>I use bootstrap monthpicker:</p>
  
  <pre><code>$("#datepicker").datepicker({
      format: "mm-yyyy",
      viewMode: "months",
      minViewMode: "months"
  });
  
  &lt;div class='input-group date' id='datepicker'&gt; 
     &lt;input type='text' class="form-control" readonly /&gt; 
        &lt;span class="input-group-addon"&gt; 
            &lt;span class="glyphicon glyphicon-calendar"&gt;&lt;/span&gt; 
         &lt;/span&gt;
      &lt;/div&gt;
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/WCtd5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WCtd5.png" alt="enter image description here"></a></p>
  
  <p>Like this picture, I chose Apr but class active add to February, and same for another month, it's always minus 2 month. </p>