function setDate(yearObj,monthObj,dayObj,dayTail) {
	if(yearObj.selectedIndex > 0 && monthObj.selectedIndex > 0) {
		timeA = new Date(yearObj.options[yearObj.selectedIndex].value, monthObj.options[monthObj.selectedIndex].value,1);
		timeDifference = timeA - 86400000;
		timeB = new Date(timeDifference);
	
		var daysInMonth = timeB.getDate();

		var daySelectIndex = dayObj.selectedIndex;
		dayObj.length = 1;

		for (var i = 1; i <= daysInMonth; i++) {
			dayObj.options[i] = new Option(i + " " + dayTail, i);
			if(i == daySelectIndex) dayObj.options[i].selected = true;
		}
	}

	//dayObj.options[0].selected = true;
}