A model of the chronology of the universe, scaling the scientifically accepted age of 13.8 billion years down to a single year, with the Big Bang taken as January 1 and the present moment taken as December 31.

A clock that also displays the date

The republican calendar used for twelve years in revolutionary France (from late 1793 to 1805).

A non-repeating, vigesimal (base-20) and base-18 calendar used by the Maya and several other pre-Columbian Mesoamerican cultures