I got the idea from this pattern which I think thedarlingone posted about last year, but I had a couple issues with that pattern, firstly that I don't believe in bookshelves that have that much empty space on them, and secondly that there were so many more opportunities to encode data that they weren't using!!!

So mine is basically not based off a pattern; I pulled the colors out of my leftovers box and I'm working from the bottom up instead of top down, since I don't know how high any given month will need to be. (And there isn't going to be any room for knicknacks; I already used up most of the spare February shelf space cramming in the super-tall book from the 11th on the diagonal.)

I haven't figured out what the actual shelf will look like, I figure that can come last.