Computing Number of Days between Two Dates in XSLT 1.0

I am looking for an XSLT 1.0 template that computes the number of days
between two dates.  I don't want to reinvent the wheel, but I was unable to
find such a template browsing around in Google.  Can anyone post or point me
to one?

I know there is an EXSLT date:difference template that computes the duration
between two dates, but it can include years and months.  It is not a trivial
task converting these components of a duration to the number of days, as I
would have to take into account leap years and the different number of days
in each month.

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Roger L. Cauvin
r o g e r @ c a u v i n . o r g
http://cauvin.blogspot.com