Layout
Basically the calendar cube has the basic functions of a normal 3x3x3 Rubiks Cube except that only one surface needs to be solved in order to display the day of the week, the month and the date. It's a tiny bit more tricky than the standard 3x3x3 if you'd only want to solve one surface since the edge pieces need to have the right orientation. However, since we only solve one single surface, solving the 3x3x3 Rubiks Calendar Cube is extremely easy and can be learned in just a few minutes.
I will be using Singmaster notation throughout this document. If you're not familiar with it, just follow the link to Wikipedia - it's no big deal.
Overview
The basic solution is: Move from inside to the outside. This means, first solve the middle piece, then edges and then the corners. In this solution I'm going to solve for Saturday May the 16th, which is my wedding day :-)
Step 1: Middle piece
The first step is to locate the middle piece you need in the right orientation. This is really easy. All it means is that web you're in May, you're going to look for the "A" of "MAY" and turn it in the right direction.
Step 2: Edges
This again is pretty easy as you can move around the side you're solving: say you're solving the "Y" of "MAY" then you can freely move the complete right side and the backside of the cube. First, place all pieces which contain the text you need in their appropiate locations. This means you're going to move the edge piece "day" to the top, the "M" piece to the left, the "Y" piece to the right and the "1" piece to the bottom (remember, we're solving Sat, MAY 16th). Note that they do not yet have to be in correct alignment so far. this means that you can move the edge piece which has "M" and "F" on its sides to the left without having to worry about getting the "M" - not the "F". We'll come to that in a second. When you're done what you should have should look like this (not particularly the flipped "day" top piece, the flipped "M" left piece and the flipped "1" bottom piece):
Now to orient a piece, you're going to rotate the cube so that the piece you want to flip is at the right side. Then, perform the following algorithm:
R' b R'
Or in words, if you didn't read the notation link above: Move the right side towards you, move both back layers counterclockwise and then again move the right side towards you. This will get you from this (pay attention to the "B/Y" piece):
To this:
And again, before and after (flipping the "3/1" piece):
Do this for all four edges.
Step 3: Placing corners
Now this is the last step, we're almost there. First, we're going to place all four edges again without worrying about their orientation (this is the next step). To do this, we always hold the cube in a way that the piece we want to set is at the front top left front and the piece we want to put in it's place is in the top back right. Then, perform:
L' B L
Or, again in plaintext: move the left side away from you, move the back counterclockwise and move the left side again towards you. This is what you should end up with:
Do this with all four corners. In the above example you will notice that the "Satur" piece has already correct orientation and the empty piece on the bottom left also has. The two pieces on the right side (one empty piece and the "6" piece) are oriented wrong - we will fix this in the next step.
Step 4: Orienting corners
Ok, this is the last step. Hold the cube so that the corner of which you want to change the orientation is in the upper right corner. Then, perform this algorithm:
R B R' B' R B R'
This should flip it in one direction. If you need to flip it in the other direction, you can either perform the above algoritm twice or you can do:
R B' R' B R B' R'
Which will be the reverse of the above. What you're performing is this (take a look at the "Mon/Fri/ " corner piece):
Or this (take a look at the "0/6/ " corner piece):
Try not to memorize it by the letters (I sure can't!), but instead memorize what you're actually doing:
- R B R': You're moving the top upper right piece in the top back left corner.
- B: You're moving the piece to the top back right corner so it will move in the next step and change it's rotation.
- R B R': You're again moving the piece from the top back right corner in, with it's changed rotation.
Just do this for all four corner pieces and you're done! :-)
Broken cube?
I've already seen calendar cubes that cubes had wrong stickers placed. Consequently, they were not solvable for every date. This is a really annoying thing and unless you're a genius it's quite difficult to tell if you deal with a broken cube or a working one. So after I got my replacement cube, I wrote this Python script to check if all possible combinations were possible (there may be really subtle bugs in the cube which you might not notice immediately). To enter your cube placement, just adapt the source code (which I commented somewhat in the relevant places). I release the software under the terms of the GNU GPL-2.