date/time EXSLT functions "not available"

[Chris]

Can someone point me the right way? I'm trying to use the date/time
extensions but with little luck. Here's what I've got:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:date="http://exslt.org/dates-and-times" >

<xsl:template match="/" >
date-time: <xsl:value-of select="date:date-time()"/>
<!-- year: <xsl:value-of select="date:year()"/> -->
</xsl:template>
</xsl:stylesheet>

If I execute this I get:
<?xml version="1.0" encoding="UTF-8"?>
date-time: 2005-09-18T22:05:57-05:00

...which is reasonable. However, if I un-comment the year line I get:
XalanXPathException: The function number
'http://exslt.org/dates-and-times:year' is not available.
(file:///D:/support/xml/date-test.xslt, line 8, column 47)
I can't seem to call any date-time function other than date-time.

Why?

I'm using Xalan-C++ 1.9.

Thanks very much...
Chris