[Zope-dev] Can I create dtml to calculate a date 30 days ago?

[jpenny@universal-fasteners.com]

I would like to do the following:
<dtml-call "REQUEST.set('magicdate', DateTime()-days)">
where days is a variable set in a form in a higher level
web page.  It does not work, complains about 
"bad operand for unary -".

Is there a way in DTML to do this?
(And if so, what is it?).

I am usually pretty good at trying quoting variants until I
stumble accross one that works, but I just can't find it this
time.

Thanks

Jim