function daySet(obj, y, m, d) {
	var tday = new Date(y,m,0);
	var cnt=0;
	obj.options.length=cnt;
	for(i=1; i<=tday.getDate(); i++){
		newItem = new Option(cnt);
		obj.options[cnt] = newItem;
		obj.options[cnt].text = i;
		obj.options[cnt].value = i;
		if(i==d) obj.options[cnt].selected = true;
		cnt++;
	}
}