[xsl] xslt 2.0 calendar

I'd like to be able to generate a simple calendar using the xslt 2.0
date/time functions.

Is there a way to know:

1. How many days are in a given month?
2. How to add a duration to a given date (e.g. add a day to '2006-03-31'
to produce '2006-04-01')?

There appears to be lots of new date formatting, extraction and duration
functions in the xslt 2.0 spec but I can't find any that achieve the
above.

I'm using Saxon 8.7.

Any help much appreciated.

David Murphy