The Aztec calendar is a timekeeping system that was used in the Mesoamerican Aztec culture and by other peoples of the pre-Columbian era in Central America. The calendar is sometimes referred to as the Sun Stone, due to the imagery depicted on the carved basalt. The original name that was used historically by the Aztecs, however, is cuauhxicalli (“eagle bowl”). The original Aztec calendar was carved into a slab of basalt weighing more than 22 metric tons, and was found in 1790 in the main square in Mexico City. The carving is currently housed in the National Museum of Anthropology and History in Chapultepec Park in Mexico City.
The Aztec calendar was a complex counting of days and years that involved two cycles: one consisting of 365 days based on the solar year, and the other consisting of 260 days, which may be based upon the Aztecs’ obsession with numerology. Together, when all the combinations of the cycles were exhausted and formed a 52-year “century,” the combined cycle culminated with an elaborate ritual by the Aztecs known as the New Fire Ceremony, which helped stave off the end of the world.
The 365-day count (xiuhpohualli in Nahuatl) consisted of 18 months divided into 20-day periods, with the remaining 5 days known as Nemontemi. The days in Nemontemi were considered unlucky, and were filled by fasting, in the belief that nothing good would come by attempting anything productive. Whether the Aztecs placed these 5 days at the end of the calendar year, throughout the year, or at the beginning is unknown, but it is certain they were there.
Each month in the xiuhpohualli had a name and corresponded to a deity in Aztec mythology. Because human sacrifice and ritualized warfare were a religious necessity in Aztec culture, many of the months are characterized by the types of human sacrifices and actions performed. These sacrifices would be performed on the Sun Stone itself. For example, in the month of Hueytozoztli (great vigil), the patron deities Centeotl and Chicomecacoatl were appeased with virgin sacrifices. At this time of the year occurred the blessing of the maize, with which both Chicomecacoatl and Centeotl were associated.
The 260-day count (tonalpohualli) consisted of 20 periods of 13 days (trecenas), each given a particular sign. These included, in order: caiman, wind, house, lizard, serpent, death’s head, deer, rabbit, water, dog, monkey, grass, reed, jaguar, eagle, vulture, motion, flint knife, rain, and flower. The periods would begin sequentially, assigning a number to each symbol (i.e., 1 caiman, 2 wind, etc.), until after the 13th day, when the beginning of a new trecena
would be marked 1, with whatever symbol with which it was associated.
The tonalpohualli is very important for the Aztec mindset. Not only does it serve as a divinatory tool, but it also serves as a time division for a particular deity. The Aztecs believed in an equilibrium that pervaded the cosmos. It was their duty to maintain that equilibrium. Since the deities of the Aztecs are always battling for power, everything needs to be divided up among them (including time) to prevent the disruption of the equilibrium.
In order to prevent confusion of years, the Aztecs named a new year with the symbol of the last day of the last month of the year. These 4 days could be represented only by the glyphs for reed, flint knife, house, and rabbit. Subsequently, in the 52-year century, the numbers 1-13 would apply to each of these four glyphs, depending on the year count (i.e., if the previous year was 1 reed, the next would be 2 flint knife). This would continue until the 13th year, and then a new glyph would be assigned to the year as 1 (in the above cycle it would be 1 flint knife). In order to avoid confusion with days, the date would be written with the year boxed in. An Aztec day would be represented as its tonalpohualli counterpart (e.g., 1 caiman) in its year (e.g., 1 reed). At the end of the 52-year cycle, the process would begin anew, with the year reverting to 1 reed.
The Aztec calendar, as it has come to be known, remains significant to many scholars interested in mathematics, anthropology, archaeology, and cosmology. It offers insights into both the religious and the agricultural life of not only the Aztecs, but also other Nahuatl peoples who used a similar system. Though it remains under a museum’s custody, the calendar still keeps its count, endlessly repeating its 52-year cycle.
See also Mayan Calendar; Measurements of Time
Graeber, R. B., & Jimenez, R. C. (2006). The Aztec
calendar handbook (4th ed.). Saratoga, CA: Historical Science Publishing.
Holmer, R. (2005). The Aztec book of destiny. North Charleston, SC: BookSurge Publishing.