erm, unless I'm missing something - you hardly need a module for this. All you need to do is look at the latitude value. If it's negative (Southern Hemisphere), then the seasons fall on one set of dates. And if it's positive (Northern Hemisphere), then they are reversed. Of course, this doesn't account for the polar, tropical and various other regions which don't really have four seasons - but your question didn't mention that.

cheers,
Darren :)