[Zope] Converting from week no. to date

[Jonas Nielsen]

DateTime().strftime("%U") converts from date to week no.

Is it possible to convert from (week,year,weekday) to a specific date in 
a python script in zope ?

I could install the mx.DateTime module in python and then make a product 
with a method that used ISO.Week() but is there a more straight forward 
approach ?