How does this calendar thing even work? I was enjoying my lunch over the 8th episode of YuriYuri and right at the beginning there was this unusual calendar:



Truth be told, this is the first time I see a calendar like that. As you can see, it consists of 3 parts which seem to be made of wood. The lower part says "April", so I assume it is removable so that the cubes above it can rotate, and that there are 11 more like it somewhere else in store.

Now the tricky part is the numbers. The 2 blocks on top are set up to read "01" which is for April the 1st. But the top side of the block that reads 0 in front, has a 6 on it. What's going on? And there are only 4 sides that can be rotated with their front sides for each digit to form a number of a day of the month. Is this an animation mistake? If not, how can this calendar thingie work?

Also, is it even possible to make them read all numbers from 01 to 31?
With two cubes, you don't have enough sides (total 12) to give both cubes numbers 0-9.

Instead, each cube has its own numbers (there may be other permutations that work, too):


One cube (A) will have 0, 1, 2, 4, 5, 6.
The other (B) will have 0, 1, 2, 3, 7, 8.


Then each date is represented by how the cubes are used:


01-03: Cube A is 0, followed by cube B.
04-06: Cube B is 0, followed by cube A.
07-08: Cube A is 0, followed by cube B.
09: Cube B is 0, followed by cube A, on 6, upside-down.
10-13: Cube A is 1, followed by cube B.
14-16: Cube B is 1, followed by cube A.
17-18: Cube A is 1, followed by cube B.
19: Cube B is 1, followed by cube A, on 6, upside-down.
20-23: Cube A is 2, followed by cube B.
24-26: Cube B is 2, followed by cube A.
27-28: Cube A is 2, followed by cube B.
29: Cube B is 2, followed by cube A, on 6, upside-down.
30-31: Cube B is 3, followed by cube A.


And before you ask, no, I've never seen one of these, and thus I really have no citation. But given the fact that the cubes look like they can go in either order (since they have numbers on the side, they should come completely free), this seems like the most logical solution.