Aztec Calendar System

Timeline

1. 1300–1320Tenochtitlan · Valley of MexicoAfter founding their capital on islands in Lake Texcoco, the Mexica inherited and integrated the dual 260-day and 365-day calendar systems common across Mesoamerica, with the priestly class responsible for calculating ritual dates and agricultural seasons.
2. 1321–1330Templo Mayor (Tenochtitlan) · Valley of MexicoDuring the consolidation of the Aztec Triple Alliance in the 1420s–1430s, the priestly class presided over sacrifice cycles scheduled by the dual calendars at the Templo Mayor, making calendar computation core knowledge for sustaining royal legitimacy and agricultural order.
3. 1427–1519Tenochtitlan · Valley of MexicoAt the empire's height, large calendrical and ritual stone carvings such as the Sun Stone were completed, depicting cosmic eras, calendar cycles, and blood-sacrifice theology in pictorial form, becoming the most representative material expression of Aztec temporal cosmology.
4. 1521Valley of Mexico · Valley of MexicoAfter the fall of Tenochtitlan, colonial authorities imposed the Christian era and the Gregorian calendar, officially abolishing the Aztec dual-calendar system; some calendrical knowledge continued covertly in indigenous communities through codices and oral transmission.