title: jquery datepicker: validate date
body: <p>i have set a jquery class:</p>
  
  <pre><code>$(function() {
              $( ".datepickerIT" ).datepicker({
                  showOtherMonths: true,
                  selectOtherMonths: true,
                  showAnim: "clip",
                  dateFormat: "dd/mm/yy",
                  minDate: "01/01/1925",
                  maxDate: "31/12/2050",
                  changeMonth: true,
                  changeYear: true,
                  yearRange: "1925:2050",
                  regional: "it"                      
              });
          });
  </code></pre>
  
  <p>I want to add a date check control that alert if user input not is a valid date</p>
  
  <p>How can add to the class ".datepickerIT" a check like this?</p>
  
  <pre><code>onClose: function(dateText, inst) {
          try {
              $.datepicker.parseDate('dd/mm/yy', dateText);
          } catch (e) {
              alert(e);
          };
  </code></pre>
  
  <p>And what plugin i must include into head section? </p>