This is how I made this calendar.
1) I purchased the calendar white board from Target. I believe it was under $10. You could actually make your own with white board from your local hardware store, and either writing the calendar on with sharpie or using vinyl. I didn't feel like being that crafty, & I was afraid if I added one more step, I would go another year without a calendar. (Not good at all!)
2) For the frame, I purchased 2 plain 1" x 3" pine boards & 1 furring strip from my local hardware store.
3) I cut the 1" x 3" to fit, using my miter saw, and nailed them to the front of the calendar, after applying some clear liquid nails to the edge (just to give it some added bonding).
4) I then cut the furring and applied to the back all the way around the frame. This made the sides flush with the wall.
5) The only thing left to do was paint and hang it up. Really, it was that easy.