So THAT is what the Calendar does...
I think extra turns are the most important thing to have, so I'd personally place the Calendar before the Meat Tree. Of course, I'm only one member of the clan, so I'd need the input of everyone else:
WHAT ITEM SHOULD I (OR MB) BUY NEXT?
1: Book of Magicalness (30,000 Meat)
2: Swimsuit Calendar (50,000 Meat)
3: Meat Tree (50,000 Meat)
~I.S.~