function up_date(){
    var update = new Date(document.lastModified);
    var theMonth = update.getMonth() + 1;
    var theDate = update.getDate();
    var theYear = update.getFullYear();
    theYear = theYear - 1988;
    document.writeln("平成" + theYear + "年" + theMonth + "月" + theDate + "日");
}