Here is the idea I found from Kiki Creates:
It's a flip calendar or countdown (depending on how you want to use it). All of the instructions can be found here. She has free printables for it made for September, October, November, and December.
I made mine a countdown but it can be modified for anything!
I also added two bird ornaments for her bird tree collection (only one is pictured, though).
And thank you to Louanne from My Kindergarten Kids for my "Joy" art!