Puzzle Flaw

Got this calendar puzzle as a bit of a joke present for my son in Feb, and between us we have only managed to get the date right about four or five times. Absolutely no idea if every permutation is possible. Discovered a flaw on this date; if you put it on its stand rather than lying it flat, then the piece top left drops down to reveal the wrong date.  Maybe today's solution is not unique (well yesterday's now as this post is a bit late).