Getting lastModified datetime of xml in xsl

[Tolstoy]

Hello.

I have an XML document that calls on an XSL stylesheet. I want to use the stylesheet to write to its output the date that the XML file was last modified.

I've tried various tricks with
<script type="text/javascript">
document.write("Last modified on " +Date())
</script>
embedding the document.write in the XML or in the XSL, but at each attempt I just end up writing the date that the XSL was last modified.

I'll be very grateful of any pointers.

Thanks,
Tolstoy.