จะเขียน datepicker ยังไงให้มันบวกวันที่ให้เองอัตโนมัต

<script>
  $(function() {
    $( "#from" ).datepicker({
      dateFormat:"yy-mm-dd",
      defaultDate: "+1w",
      changeMonth: true,
      numberOfMonths: 2,
      onClose: function( selectedDate ) {
        $( "#to" ).datepicker( "option", "minDate", selectedDate );
      }
    });
    $( "#to" ).datepicker({
    	dateFormat:"yy-mm-dd",
      defaultDate: "+16w",
      changeMonth: true,
      numberOfMonths: 2,
      onClose: function( selectedDate ) {
        $( "#from" ).datepicker( "option", "maxDate",selectedDate );
      }
    });
  });
  </script>

<p>
<label class="right_label" for="from" name="start">From</label>
<input type="text" id="from"  name="start"/>
to
<input type="text" id="to" name="end" />
</p>

$('#from').datepicker({
		  dateFormat:"yy-mm-dd",
		  defaultDate: "+1w",
		  changeMonth: true,
		  numberOfMonths: 2,
		  onClose: function(selectedDate) {
			  var date2 = $(this).datepicker('getDate');
			  date2.setDate(date2.getDate()+7);
			  $('#to').datepicker('setDate', date2);
		  }
  });