Displaying Year

I searched the forum on how to display a year. What I want to do is include the code so that the copyright year will automatically change without me manually changing it every year. I found the following code when doing a search in codingforums. Can I use this code on my site?

<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
var year=new Date().getYear();
if ( window.ActiveXObject ) {
document.write("" + year + "");
} else {
document.write("" + parseInt(year + 1900) + "");
}
// End -->
</SCRIPT>

Also, some sites have the original year the website was created for the copyright. Others have the current year, and yet others have the created year thru the current year. Is there any 'rule' on what is supposed to be displayed?