I found this idea of a calendar that fits into a CD case. You have to take the CD holder out, & flip the lid over backwards so it will recline. (Sorry I didn't take a picture of this part)
The base is cut at 5"x4 5/8".
Each calendar is printed onto business cards & held on with sticky photo corners so they can be changed out.
I am not going to add labels to this, if you want to know where the cut came from, please comment & I will be more than happy to share it with you.
Here is the site with each month individually: