Help splitting mail archives

Hello, 

I was wondering if one of you formail experts can help me with the
following problem.  I have a huge majordomo archive for a mailing list.  I
want to separate it into several different files by the month in which
they were sent.  How can I do this using formail? 

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Derrick Green
eusdegr(_at_)wser(_dot_)ericsson(_dot_)se
Richardson, Texas