Mesoamerican (Mayan, others) 260 day calendar cycle, shown as interlacing moving faces agaist a steady hand.
The mesoamerican cultures had a fascinating calendar system based on interlocking cycles of 13 and 20. (Tzolk’in to the Maya, Tonalpohualli to the Aztec, and probably other names to other cultures.) Unfortunately, this only accounts for 260 days, so it was usually combined with a solar year counting system based on similar principles, but using a more traditional month/day arrangement. (The Haab) The combination of dates between the two systems repeated every 52 years, which became a time of major celebration.
Disk Clock takes the idea of clock and turns it inside-out by moving the faces instead of the hand. Disk Tzolk'in shows the 13/20 interlocking cycle together with an entire 260 day disk. Outer disk relates the two cycles by alternating, overlapping colors.