/* calculate departureDate, based on arrivalDate */
function checkDepartureDate(obj) {
	/* get date string from textfield */
	var arrivalDateString = document.searchHotelPronto.arrivalDate.value;

	/* parse day,month and year from date sting */
	var datePattern = /(\d+)\/(\d+)\-(\d+)/;
	var arrivalDateDayParsed = arrivalDateString.match(datePattern);
	
	var arrivalDateDayDay = arrivalDateDayParsed[1];
	var arrivalDateDayMonth =  arrivalDateDayParsed[2];
	var arrivalDateDayYear =  arrivalDateDayParsed[3];
	
	/* construct a Date object from arrivalDate */	
	arrivalDate = new Date();
	arrivalDate.setDate(arrivalDateDayDay);
	arrivalDate.setMonth(arrivalDateDayMonth-1);
	arrivalDate.setYear(arrivalDateDayYear);
	
	/* get selected numberOfNights */
	var index = document.searchHotelPronto.numberOfNights.selectedIndex;   
	var numberOfNights = document.searchHotelPronto.numberOfNights[index].text;

	/* add numbers of days to find departure date */
	var departureDate = addDays(arrivalDate,numberOfNights);
	
	/* create a string representation for the user */
	var departureDateString = departureDate.getDate() + "/" +(departureDate.getMonth()+1) + "-" +departureDate.getFullYear();

	/* output departureDate to textfield */
	document.getElementById('calculatedDepartureDate').innerHTML = departureDateString;
	
}

function addDays(arrivalDate,days) {
    return new Date(arrivalDate.getTime() + days*24*60*60*1000);
}