function tinhngay(ngayhientai,endDate)
{
	var arrNgayHienTai = new Array();
	arrNgayHienTai = ngayhientai.split('/');
	var dateHienTai = new Date(arrNgayHienTai[2], arrNgayHienTai[1] - 1,arrNgayHienTai[0]);
	var valueradio=0;
	var vRadio = document.stepone.radioquarter;
	var endDate = document.stepone.txtendday;
	for(var i = 0; i < vRadio.length; i++) 
	{
		if(vRadio[i].checked) 
		{
			valueradio=vRadio[i].title;
		}
	}
	if(valueradio != 0){
		var sothang = parseInt(valueradio);
		var nYear = dateHienTai.getFullYear();
		var nMonth = dateHienTai.getMonth() + 1;
		var nDate = dateHienTai.getDate();
		if((nMonth + sothang)  > 12 ){
			nMonth = nMonth + sothang - 12;
			nYear = nYear + 1;
		}else{
			nMonth = nMonth + sothang;
		}
		//dateHienTai.setTime(dateHienTai.getTime()+songay*24*60*60*1000);
//		endDate.value = (dateHienTai.getDate()) + '/' + (dateHienTai.getMonth() + 1) + '/' + (dateHienTai.getFullYear());
		endDate.value = nDate + '/' + nMonth + '/' + nYear;

	}else{
		alert('Vui long chon quy !');
	}
	
}