Perpetual flip calendars have been around for a while. They seem operate very simply, but I could not for the life of me figure out how! After some digging, I found two US patents as really good references of how this mechanism works:
It was a little math problem figuring out how to evenly represent 1 through 31 using three different types of wooden tiles. I wanted to do this to be able to see how the tiles flowed through the calendar.
I probably should have made both sides of the calendar with the acrylic windows just to make it look move balanced and symmetrical, but I wanted a “how does this work” side and a “this is how it works” side.
I didn’t show it here, but you can count downward if you flip the calendar the opposite way. You can also “reprogram” the calendar to flip the opposite way if you wanted to turn it towards yourself to iterate.