For the bottom block, I made a removable tag for each month (just cardstock, distressed and matted on scrapbook paper--font Mr. Giggles), which makes it so easy to just change it out every month. I thought about making 6 bottom blocks, and putting vinyl on each side--then changing out a block every 2 months. You could still do that if you prefer, but I really wanted to go with simple, and reduce the amount I had to store. To stick on the month, I actually used a little bit of double stick tape--it comes off the mod podged surface pretty easily. (In the process of making it, I added and removed a month at least 10 times, and it always worked well.)
I actually made this one for a gift, so if you're name starts with an A, and you live in Idaho, please act surprised. :) (And forgive me for not getting it mailed before Christmas--with 5 sick little ones, it was all about survival.)
Calendar Block Specifics
Wood: 4x4 posts, cut into 2 square blocks, 2x4--7 inches
Number Placement: Block 1--0,1,2,3,4,5
Block 2--0,1,2,6,7,8 (6 doubles as the 9, so make sure you put it on non-directional paper)
Paint your blocks, mod podge desired paper, sand and distress block edges, add numbers!