On my current project we use in BPEL the data type duration to define the period that a user has to execute a task, before escalating. In xpath 2.0 there is a function:
add-dayTimeDuration-to-dateTime(xs:dateTime,xs:dayTimeDuration)
This function returns a new datetime with the added duration. It works great if you are working with period longer then 1 minute. We discovered this when the duration was just a few seconds. The xslt executed without any error but the result was an invalid xml. When we changed the period from 1 sec to 1 min the transformation works as expected. So keep this in mind when using this function.
read more about xpath 2.0 functions:
http://www.w3.org/TR/xpath20/
