Mine is more of a rectangle, with the first six months on top, and the last six months on the bottom. December is in the lower left, January is above it; with the months going chronologically clockwise around the shape. The months January through April are compressed somewhat (except when I am in them, when they are stretched). June through August are bigger, November and December are smaller. They're also colored differently, and the months at the end of the year are darker.
I would be surprised to find this is rare. I certainly don't think it is synesthesia.
I would be surprised to find this is rare. I certainly don't think it is synesthesia.