The Tōnalpōhualli, meaning “count of days” in Nahuatl¹⁾, is a Mexica version of the 260-day calendar in use in pre-Columbian Mesoamerica. This calendar is solar and consists of 20 13-day periods called trecenas. Each trecena is ruled by a different Teotl. Different graphic representations for the twenty day names have existed among certain ethnic, linguistic, or archaeologically identified peoples.

Because it only consists of 260 days, there are no fixed dates on the Tonalpohualli that can be correlated yearly to Gregorian dates. Where the 360 day Xiuhpohualli can be used to fix dates and track seasons, the Tonalpohualli can instead be used to describe and contextualize those dates, and to track certain sacred days such as the birthdays of Teteoh. The calendars serve different functions and complement each other.