Aztec Calendar Calculator (Your Aztec Day Sign in the Tonalpohualli)

How it works

Days since 13 August 1521 (Julian calendar), the fall of Tenochtitlan = 1 Coatl (Caso correlation) · number = (days mod 13) + 1 · sign = (days + 4) mod 20, counting Cipactli = 0 … Xochitl = 19 · position in the 260-day tonalpohualli = (days + 104) mod 260 + 1

The Aztec (Mexica) tonalpohualli is a sacred count of 260 days that combines the numbers 1 to 13 with twenty day signs, from Cipactli (crocodile) to Xochitl (flower). The sign of the day you were born, your tonalli, was believed to shape your destiny, and each sign has a patron deity and a cardinal direction. To place modern dates on the Aztec count, the calculator uses the correlation of Alfonso Caso, based on the Spanish record that Tenochtitlan fell on 13 August 1521, the Aztec day 1 Coatl (1 Serpent). Popular "Aztec horoscope" tables that assign signs by month and day of the month are a modern invention; this is the actual day count.

Worked example

Counting the days from 1 Coatl (13 August 1521 in the Julian calendar), November 3, 1992 falls on 9 Mazatl: number 9 and the sign Mazatl (Deer), whose patron is Tlaloc and whose direction is West. It is day 87 of the 260-day count, in the trecena that began on 1 Quiahuitl (Rain), and the next day is 10 Tochtli (Rabbit).

Sources: Caso, Alfonso — Los calendarios prehispánicos (UNAM, 1967) · Encyclopaedia Britannica — Tonalpohualli

Frequently asked questions