I love the idea of a perpetual calendar, and I love shadow boxes, so I combined the two to make a shadow box calendar. The day numbers store on top and the month tags in a box on the back.
The box is made with 1 sheet of 1/4" maple (and a scrap of another) and the date/month tags made from 1/8" wood. I cut the numbers from 1/16" wood (because the number blocks are two-sided); you could probably use 1/8" wood, but it may be a little too chunky.
Right now, I’ve finished 12 different inserts, (haven’t photographed them all) with many more rattling around in my head. The inserts are made with a variety of 1/4", 1/8", and 1/16" wood pieces. They make a fun DIY project.