Aztec Calendar
The Tonalpohualli is the 260-day Aztec calendar, built on the same principle as the Mayan Tzolkin: twenty day signs and the numbers 1 to 13. The names of the signs and the patrons differ, but the math is the same.
Today: November 7, 2026
This is a chosen day: the sign and number describe the character of the day itself.
Full name of the day: 3 Atl. It is day 3 of 13 in the trecena. Meaning of the Atl sign →
In the Maya Tzolkin the same day is 3 Muluc: Muluc seal →
The count is aligned with the Maya Tzolkin using the Goodman–Martínez–Thompson correlation (GMT, 584283). Researchers also use other correlations; the difference is one or two days.
How the Calendar Works
Twenty signs, from Cipactli, the crocodile, to Xochitl, the flower, run in a circle, and alongside them runs a count from one to thirteen. The combination repeats every 260 days.
The cycle was divided into 20 periods of 13 days, which scholars call trecenas: each had its own patron and its own character. In addition, the Tonalpohualli meshed with the 365-day solar year, and the full alignment of the two calendars produced a 52-year cycle, the "bundle of years," which the Aztecs marked with the New Fire ceremony.
What the result means
The calculator shows the day sign and a number from 1 to 13.
The sign sets the theme: water, house, movement, knife, rain. Each had a patron god, and priests read the day as a combination of these influences. All twenty day signs.
The number works like the tone in the Mayan system: it shows the stage and the strength. Days with high numbers were considered stronger, but not necessarily more favorable.
Among the Aztecs, the calendar also determined a child's name: a person was named after their day of birth, hence names like Ce Acatl, "One Reed."
Accuracy and Correlation
A caveat is needed here. The correspondence between Aztec and European dates has been reconstructed from records of the Conquest era, and researchers disagree by a day or two: different correlations give different results.
Our calculation is aligned with the Mayan Tzolkin using the GMT correlation 584283, so Cipactli corresponds to Imix. This is a common method of matching, but not the only one, and other approaches appear in academic works.
Frequently asked questions
How is the Tonalpohualli different from the Tzolkin?
Mathematically, it isn't: the same 20 by 13. What differs are the names of the signs, the patron gods and the tradition of interpretation.
Is this the famous "Aztec calendar"?
No. The stone disk everyone knows from photos is the Sun Stone, a monument with a cosmological theme, not a working calendar.
Can it be used to predict the future?
The Aztecs used it to choose days for rituals, war and naming. Modern predictive interpretations are a later addition.