title: how to reject the selected date in onSelect in jquery ui DatePicker
body: <p>I have a web-form where I'm asking the user for several dates. Usually, <em>but not always</em>, a repeated date will be a human error.  So in the onSelect function I'm checking to see if the date has already been entered, and asking the user to confirm whether a duplicated date was intentional. If the user says No, how to clear the date value from the picker?</p>
  
  <pre><code>// datesList initialized in outer scope
  
  onSelect: function (thedate, picker) {
  
  
       if ($.inArray(new Date(thedate).valueOf(), datesList) == -1) {
          //store chosen dates in datesList if we haven't seen it before
          datesList.push(new Date(thedate).valueOf())
  
         } else {
              // ask the user if it was intentional
              //if unintentional, reject the choice and clear the picker
  
  
         }
  
      }
  </code></pre>