myModify = document.lastModified;
myD = new Date(myModify);
myYear = myD.getYear();
myYear4 = (myYear < 2000) ? myYear+1900 : myYear;
myMonth = myD.getMonth() + 1;
myDate = myD.getDate();
myStr = "更新日: " + myYear4 + "/" + myMonth + "/" + myDate;
document.write( myStr );