function update() {
	date = new Date();
	yy = date.getYear();
	mm = date.getMonth() + 1;
	dd = date.getDate();
	if (yy < 2000) { yy += 1900; }
		if (dd > 1) {
			dd -= 1;
		} else {
			if(mm == 3){
				mm -= 1;
				dd = 28;
			} else if(mm == 5 || mm == 7 || mm ==10 || mm == 12) {
			  mm -= 1;
				dd = 30;
			} else {
				mm -= 1;
				dd = 31;
			}
		}
	document.all.update.innerHTML = yy + "年" + mm + "月" + dd + "日" + "更新";
}