dateTime duration with XSLT in SOA 11g

This tiny post reminds me the exact reason why I started this blog. I want to collect the things I learned using SOA.

It took me a long time to figure out this tidbit with XSLT before, but I just spent half a day to re-figure it out again. 

In my XSLT I need to calculate the duration based on two dateTime fields. So I used this expression:
    <xsl:variable name="dur">
      <xsl:value-of select="xsd:dateTime($endDt)-xsd:dateTime($stDt)"/>
    </xsl:variable>

However, with JDEV 11g, the default XSLT stylesheet version is "1.0". The above expression doesn't work with "1.0". I have to change the version to "2.0". That's all. With that, "dur" will have a value like "PT2H5M". Then you can maniplate it.

Now I have recorded it here, so I don't have spend another 5 hours to "re-discover" it next time.