Combinatorial Perpetual Calendar

This perpetual calendar turns every day into a small mathematical puzzle. With only two numbered cubes, you can create every date of the month — a simple combinatorial idea that often makes visitors stop, look twice, and ask how it works.

I printed my version using ACE for multicolor printing, but a non-ACE version is also included, so the model can be printed on a standard single-material printer as well.

The raised numbers are designed to press-fit into the cubes. Depending on your printer calibration and settings, some may fit tightly while others may need a small drop of glue to stay securely in place.

A simple desk calendar, a conversation piece, and a little bit of mathematics to solve every day.