สอบถามเกี่ยวกับการใช้ jquery datepicker ครับ คือมี startdate กับ enddate จะให้มันคำนวณกัน

<script type="text/javascript">
/* create an array of days which need to be disabled */
var disabledDays = ["5-1-2012","5-16-2012","2-27-2010"];

/* utility functions */
function nationalDays(start_date) {
	var m = start_date.getMonth(), d = start_date.getDate(), y = start_date.getFullYear();
	//console.log('Checking (raw): ' + m + '-' + d + '-' + y);
	for (i = 0; i < disabledDays.length; i++) {
		if($.inArray((m+1) + '-' + d + '-' + y,disabledDays) != -1 || new Date() > start_date) {
			//console.log('bad:  ' + (m+1) + '-' + d + '-' + y + ' / ' + disabledDays[i]);
			return [false];
		}
	}
	//console.log('good:  ' + (m+1) + '-' + d + '-' + y);
	return [true];
}
function noWeekendsOrHolidays(start_date) {
	var noWeekend = jQuery.datepicker.noWeekends(start_date);
	return noWeekend[0] ? nationalDays(start_date) : noWeekend;
}

/* utility functions */
function nationalDays(end_date) {
	var m = end_date.getMonth(), d = end_date.getDate(), y = end_date.getFullYear();
	//console.log('Checking (raw): ' + m + '-' + d + '-' + y);
	for (i = 0; i < disabledDays.length; i++) {
		if($.inArray((m+1) + '-' + d + '-' + y,disabledDays) != -1 || new Date() > end_date) {
			//console.log('bad:  ' + (m+1) + '-' + d + '-' + y + ' / ' + disabledDays[i]);
			return [false];
		}
	}
	//console.log('good:  ' + (m+1) + '-' + d + '-' + y);
	return [true];
}
function noWeekendsOrHolidays(end_date) {
	var noWeekend = jQuery.datepicker.noWeekends(end_date);
	return noWeekend[0] ? nationalDays(end_date) : noWeekend;
}

/* create datepicker */
jQuery(document).ready(function() {
	jQuery('#start_date').datepicker({
		//minDate: new Date(2010, 0, 1),
		//maxDate: new Date(2010, 5, 31),
		//dateFormat: 'DD, MM, d, yy',
		showOn: "button",
		buttonImage: "images/calendar.gif",
		buttonImageOnly: true,
		dateFormat: 'dd/mm/yy',
		constrainInput: true,
		beforeShowDay: noWeekendsOrHolidays
	});
$("#end_date").datepicker({
				showOn: "button",
				buttonImage: "images/calendar.gif",
				buttonImageOnly: true,
                //minDate: +3,
				constrainInput: true,
				beforeShowDay: noWeekendsOrHolidays,
				dateFormat: 'dd/mm/yy',
				onSelect: function (dateText, inst) {

                    var date2 = dateText;
                    var date1 = $("#start_date").val();
                    date1 = date1.split("/");
                    date2 = date2.split("/");


                    sDate = new Date(date1[2], date1[1] - 1, date1[0]);
                    eDate = new Date(date2[2], date2[1] - 1, date2[0]);

					
					alert(jQuery('#sDate').val());
					alert(jQuery('#eDate').val());

                    var daysDiff = Math.round(((eDate - sDate) / 86400000)+1); //totalday + 1//
					//var daysDiff = Math.round((eDate - sDate) / 86400000);
                    $("#sumDay").val(daysDiff.toString());

                    var result = parseInt($("#day_old").val()) + parseInt($("#sumDay").val());
                    $("#txtAns").val(result);
                }
            });
});

</script>