title: Datepicker loses date value when dateFormat doesn't include day
body: <p>I have two HTML input elements. The first is a read-only text input that displays the chosen month and year, and the second is a hidden input that saves the date selected:</p>
  
  <pre><code>&lt;input type="text" id="MonthDisplay" readonly="readonly" /&gt;
  &lt;input type="hidden" name="Month" /&gt;
  </code></pre>
  
  <p>The goal is to store the actual date chosen in the hidden field, but to display only the month and year in the visible MonthDisplay field. </p>
  
  <p>Here is code to initialize the datepicker:</p>
  
  <pre><code>$('#MonthDisplay')
      .datepicker({
          'dateFormat'  : 'MM yy',
          'changeMonth' : true,
          'changeYear'  : true,
          'yearRange'   : '2010:'+new Date().getFullYear(),
          'altField'    : "input[type=hidden][name=Month]",
          'altFormat'   : "m/d/yy"
      });
  </code></pre>
  
  <p>The first time the user picks the date, everything works great. The display field and the hidden field are both set correctly. But the second time the user clicks the display field, the datepicker doesn't default to the month selected. Instead, it defaults to today's month. I'm pretty sure this is happening because the control can't parse the date -- when I set the dateFormat to include the day (using the format string <code>"dd MM yy"</code>), it works great. But I don't want to include the day in the display to the user.</p>
  
  <p>So my question is, how can I intercept the date that datepicker is using so on the second time through, the date remembers the previous month selected? </p>
  
  <p>Or, as an alternate question, is there a way to make the datepicker or another control select only the month and year without also picking the date?</p>