How would i Valiadate Datepicker is empty

How would i Valiadate Datepicker is empty

My date picker is joined into my Contact form on pressing the Submit button all fields on the form are validated ok.

how would i validate,,,,,  that a date as been selected and not submitted with an empty field. below is my code


<!-- Start of datepicker -->

  <script>
    $(document).ready(function()
     {
        $("#datepicker").datepicker();
     });
    </script>
 
   
<!--  $(selector).datepick({dateFormat: 'yyyy-mm-dd'});  for my example -->

    <script> 
        $(function() {                   
                $.datepicker.setDefaults({dateFormat: 'DD, d  MM yy', autoSize: true,
             minDate: -0, maxDate: '+1M +05D', showOn: 'button',
            buttonImage: '/contact/images/calendar.gif', buttonImageOnly: true, });
        $('input[name="Your Check In Date Is"],input[name="Your Check Out Date Is"]').datepicker();
   
    });
   
    </script>
  
   
 
    <script type="text/javascript">
        $(function(){
               
           
            $("input[name='Your Check In Date Is']").datepicker();
            $("input[name='Your Check Out Date Is']").datepicker();
        });
    </script> 
   
    
     
    <label for="datepicker">Select Your Check In Date</label>
    <form method="post" id="myForm">
   
    <input name="Your Check In Date Is" maxlength="30"  class="text ui-widget-content ui-corner-all" />
   
   
    <label for="datepicker">Select Your Check Out Date</label>
    <input name="Your Check Out Date Is" maxlength="30" class="text ui-widget-content ui-corner-all" />
   
    <!-- End of datepicker -->  
   
 

 <!-- Start of submit -->
    <div class="submit">
      <input type="submit" id="submit" name="submit" value="Click To Comfirm Your Booking Details" />
    </div> <!-- end .submit -->
<!-- End of Submit -->
   
  </form>
   <div id="footer">
<p>&copy; <?php echo date('Y'); ?>Copyright Webber's InterConinental Tours... All rights reserved.</p>
   </div><!-- end footer -->
    <?php else: ?>
<p style="font-size:35px; font-family:Arial, Helvetica, sans-serif; color:#255E67; margin-left:25px;">You are now being redirected to the secure payment site</p>

<script type="text/javascript">
setTimeout('ourRedirect()', 5000)

function ourRedirect(){
    location.href='http://philippines4u.co.uk/PayPal Manila Condo form.html'
}

</script>

<?php endif; ?>

   
</div> <!--end #form -->
</div> <!-- end formWrap -->


</body>
</html>

Have been working with this code   if($("#fieldID").val() == "") { alert("no date selected"); } But i Cant make it work.