"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!" says woodworker and YouTuber Measured Workshop, who decided to record himself building one in a nicely-edited video.

 

"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."

 

Measured Workshop describes himself as an ameteur woodworker. On his YouTube channel, he builds wooden lumber racks, USB lamps, sliding door tool cabinets, picture frames, and various jigs. We wouldn't call him an amateur.