What was the Aztec 260-day ritual calendar called?

The Aztec 260-day ritual calendar was called the Tonalpohualli, meaning “day count” in Nahuatl. It was a sacred cycle used for divination, naming, ceremonies, and determining the character or fortune associated with particular days.

The cycle combined 20 day signs with the numbers 1 through 13. Each day advanced both systems, creating 260 unique combinations before the same number-and-sign pairing returned. A day might therefore be identified by a number and a sign, rather than by a month and date in the modern sense.

The Tonalpohualli operated alongside the 365-day Xiuhpohualli, or “year count,” which was more closely connected with the solar and agricultural year. Together, the two cycles formed a 52-year calendar round. Tonalamatl is related terminology often used for a divinatory calendar or almanac, but Tonalpohualli is the standard name for the 260-day cycle itself. Ce Acatl is a calendar date or name, not the calendar’s title.