I am trying to make a report in Trac that shows all bugs grouped by month/year.  How do I do this?

Originally posted on Dreamwidth.

What I want right now is to know why it is that in Trac, when I filter on description like 'bob' and I add another description filter of 'foo', it assumes that I want tickets with 'bob' OR 'foo', and won't let me change it.