Through a series of unfortunate Wikipedia links, I ended up on the page for ‘Pataphysics. The calendar caught my eye, and I wondered how hard it would be to implement in Python.
The original French calendar is here. I had to consult that version to make sure that there are supposed to be two Sundays in a row on leap years. (29 mod 7 = 1 => Sunday, next day is 1 mod 7 = 1 => Sunday again).
You can check out my implementation on my GitHub.