Aztec zodiac sign calculator by date of birth
Find your Aztec zodiac sign from your date of birth: tonalpohualli day sign, number from 1 to 13, trecena and patron deity, with sources.
How the Aztec day sign is calculated
The Aztec sign is the day of the tonalpohualli, the 260-day Mexica ritual calendar: 20 signs combined with the numbers 1 to 13. Someone born on 15 March 1990 has the sign 7 Calli (House), in the 1 Ollin trecena, with Tepeyóllotl as patron deity.
The correlation
Chroniclers date the fall of Mexico-Tenochtitlan, 13 August 1521 in the Julian calendar, to a 1 Serpent (Cóatl) day in the year 3 House (UNAM, Noticonquista). That date is one of the supports of the GMT correlation, Julian day 584283, used for the Maya tzolk'in (Long Count on Wikipedia). The calculator applies the same correlation: it gives 1 Cóatl for that day and 4 Xóchitl (4 Ahau in Maya) for 21 December 2012.
The calculation
Count the days elapsed since Julian day 584283. The number is (days + 3) modulo 13 + 1 and the sign is (days + 19) modulo 20, starting from Cipactli. A trecena is the 13-day block that starts on a number 1 and takes that day's name.
Worked example
15 March 1990, Julian day 2447966: 1,863,683 days since the origin, 7 Calli, day 163 of the cycle, trecena 13 of 20 (1 Ollin). The patron deity of Calli is Tepeyóllotl (tonalpohualli table).
Limits
Many press lists assign a fixed sign to each date of the year. A 260-day cycle does not fall on the same date every year, so those lists agree neither with each other nor with this count. The sign is cultural heritage, not a forecast. See also zodiac sign and Chinese zodiac and the Chinese zodiac calculator.
Frequently Asked Questions
Why doesn't my Aztec sign match the one in magazines?
Many press lists give a fixed sign for each date of the year, but the tonalpohualli lasts 260 days, not 365. Each year the same calendar date moves 105 positions forward in the cycle (106 when a February 29 falls in between), so the sign changes from one year to the next.
Which correlation does the calculator use?
The GMT correlation, Julian day 584283, the same as for the Maya tzolk'in. With it, 13 August 1521 (Julian), the day Tenochtitlan fell, is 1 Cóatl, as the chronicles record.
What is a trecena?
It is a 13-day period that starts on a day numbered 1 and takes its name: 1 Cipactli, 1 Océlotl, 1 Mázatl and so on. The tonalpohualli has 20 trecenas, 20 × 13 = 260 days.
Is the Aztec sign the same as the Maya nawal?
Both follow the same 260-day cycle and their signs match: Cipactli with Imix (Imox in K'iche'), Calli with Akbal (Aq'ab'al) and so on. With the same correlation, a date gives the same number and the equivalent sign in both calendars.
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