tonalpohualli

Tonalpohualli is the 260-day ritual calendar used by the Aztec and other Nahua peoples of central Mexico. Its name in Nahuatl means the counting or numbering of days. It functioned as a system for divination, omen interpretation, and scheduling religious ceremonies, births, and other important events.

The calendar combines 20 day signs with 13 numerals. The day signs include symbols such as Cipactli (crocodile), Ehecatl (wind), Calli (house), Cuetzpalli (lizard), Coatl (snake), Mazatl (deer), Tochtli (rabbit), Atl (water), Itzcuintli (dog), and Ozomatli (monkey), among others. The numerals run from 1 to 13, so each day is a unique pairing of a number and a day sign. The 260-day cycle is divided into trecenas, which are 13-day periods ruled by successive numbers.

Historically, tonalpohualli operated alongside the 365-day solar calendar, xiuhpohualli, to form the 18,980-day cycle known as the calendar round. This larger cycle meant that a given date in the tonalpohualli could be associated with a particular xiuhpohualli date, a relationship used in ritual planning and omen interpretation. The system provided a framework for predicting auspicious and inauspicious days for actions such as warfare, agriculture, and ceremonies.

Today, scholars study tonalpohualli through pre-Columbian codices and colonial-era sources to understand its role in Aztec religion and calendrics. It remains a key concept in the study of Mesoamerican timekeeping and divination.