function addDays(date, dayAdd) {
	millisec = (dayAdd) * 86400000;
	newTime = date.getTime() + millisec;
	return new Date(newTime);
}
function setLastDay() {
	if (!isNaN(Number (document.getElementById('nights').value)) ){
		var dataEnd =  new Date();
		var sDayVal  = Number(document.getElementById('arr_date')[document.getElementById('arr_date').selectedIndex].value);
		var sYearVal = Number(document.getElementById('arr_year')[document.getElementById('arr_year').selectedIndex].value);
		var sMonthVal= Number(document.getElementById('arr_mon')[document.getElementById('arr_mon').selectedIndex].value);
		//arrive_date.innerText=this.aryGiorni[setWeekDay(sYearVal,sMonthVal,sDayVal)];
		var dataStart = new Date(sYearVal,sMonthVal-1,sDayVal,12,00,00);

		dataEnd = addDays (dataStart, Number(document.getElementById('nights').value));
		// dataEnd.setDate(dataStart.getDate() + Number(document.getElementById('nights').value));
		document.getElementById('dep_date').value=dataEnd.getDate();
		document.getElementById('dep_mon').value=dataEnd.getMonth()+1;
		document.getElementById('dep_year').value=dataEnd.getFullYear();

	} else {
			document.getElementById('nights').value="0";
			alert ("Invalid Night number");
		}
	return true;
}