EXSLT implementation in .NET

Is this off topic?
I have the following:
xmlns:date="http://exslt.org/dates-and-times" exclude-result-prefixes="date"

I get the follwing error:
Cannot find the script or external object that implements prefix 'date'.

My implementation of it looks like this:
<xsl:value-of select="date:date(.)"/>

Any ideas how to get this to fly in .NET?

Karl