Aztec calendar · Lablypedia

Tōnalpōhualli, Aztec Sacred Calendar

The tōnalpōhualli ("day count") consists of a cycle of 260 days, each day signified by a combination of a number from 1 to 13, and one of the twenty day signs. With each new day, both the number and day sign would be incremented: 1. Crocodile is followed by 2. Wind, 3. House, 4. Lizard, and so forth up to 13. Reed. After Reed, the cycle of numbers would restart (though the twenty day signs had not yet been exhausted), resulting in 1. Jaguar, 2. Eagle, and so on, as the days immediately following 13. Reed. This cycle of number and day signs would continue similarly until the 20th week, which would start on 1. Rabbit, and end on 13. Flower. It would take a full 260 days (13×20) for the two cycles (of twenty day signs, and thirteen numbers) to realign and repeat the sequence back to 1. Crocodile.

Day signs

The set of day signs used in central Mexico is identical to that used by Mixtecs, and to a lesser degree similar to those of other Mesoamerican calendars. Each of the day signs bear an association with one of the four cardinal directions.

There is some variation in the way the day signs were drawn or carved. Those here were taken from the Codex Magliabechiano.

Wind and Rain are represented by images of their associated gods, Ehēcatl and Tlāloc respectively.

Other marks on the stone showed the current world, and the worlds before this one. Each world was called a sun, and each sun had its own species of inhabitants. The Aztecs believed that they were in the Fifth Sun, and like all of the suns before them, they would also eventually perish due to their own imperfections. Every 52 years was marked out due to the belief that 52 years was a life cycle and at the end of any given life cycle, the gods could take all they had, and destroy the world.

Trecenas

The 260 days of the sacred calendar were grouped into twenty periods of 13 days each. Scholars usually refer to these thirteen-day "weeks" as trecenas, using a Spanish term derived from trece "thirteen" (just as the Spanish term docena "dozen" is derived from doce "twelve"). The original Nahuatl term was "in cencalli tonalli" (a family of days), according to Book IV of the Florentine Codex.

Each trecena is named according to the calendar date of the first day of the 13 days in that trecena. In addition, each of the twenty trecenas in the 260-day cycle had its own tutelary deity:

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Xihuitl, Aztec Solar Calendar

In ancient times the year was composed of eighteen months, and thus it was observed by the native people. Since their months were made of no more than twenty days, these were all the days contained in a month, because they were not guided by the moon but by the days; therefore, the year had eighteen months. The days of the year were counted twenty by twenty.

— Diego Durán

Xiuhpōhualli is the Aztec year (xihuitl) count (pōhualli). One year consists of 360 named days and 5 nameless (nēmontēmi). These 'extra' days are thought to be unlucky. The year was broken into 18 periods of twenty days each, sometimes compared to the Julian month. The Nahuatl word for moon is metztli but whatever name was used for these periods is unknown. Through Spanish usage, the 20-day period of the Aztec calendar has become commonly known as a veintena.

Each 20-day period started on Cipactli (Crocodile) for which a festival was held. The eighteen veintena are listed below. The dates are from early eyewitnesses; each wrote what they saw. Bernardino de Sahagún's date precedes the observations of Diego Durán by several decades and is before recent to the surrender. Both are shown to emphasize the fact that the beginning of the Native new year became non-uniform as a result of an absence of the unifying force of Tenochtitlan after the Mexica defeat.

Veintenas of the xiuhpōhualli

Xiuhmolpilli

The Mexica counted their years by means of four signs combined with thirteen numbers, thus obtaining periods of 52 years, which are commonly known as Xiuhmolpilli, a popular but incorrect generic name; the most correct Nahuatl word for this cycle is Xiuhnelpilli. The table with the current years:

Reconstruction of the Calendar

In the last century scholars have made multiple models reconstructing the Calendar.

The Xiuhmachiotl is a contemporary digital reconstruction project that presents multiple Mesoamerican calendrical systems in an integrated interface. Its implementation combines a 260-day Tonalpohualli, a 365-day Xiuhpohualli, a Venus-focused Citlalpohualli, a nine-day Night Lord sequence, lunar and Long Count displays, and additional astronomical visualisation tools. The project distinguishes between reconstructed ceremonial calendar coordinates, arithmetic mean-cycle models, and bounded ephemeris-derived planetary-event data.

Another version was proposed by Professor Rafael Tena of the Instituto Nacional de Antropología e Historia, based on the studies of Sahagún and Alfonso Caso of the National Autonomous University of Mexico. His correlation argues that the first day of the Mexica year was February 13 of the old Julian calendar or February 23 of the current Gregorian calendar. Using the same count, it has been the date of the birth of Huitzilopochtli, the end of the year and a cycle or "Tie of the Years", and the New Fire Ceremony, day-sign 1 Tecpatl of the year 2 Acatl, corresponding to the date February 22. A correlation by independent researcher Ruben Ochoa interprets pre-Columbian codices, to reconstruct the calendar, while ignoring most primary colonial sources that contradict this idea, using a method that proposes to connect the year count to the vernal equinox and placing the first day of the year on the first day after the equinox.

José Genaro Emiliano Medina Ramos, a senior native nahua philosopher from San Lucas Atzala in the state of Puebla, proposes a multidisciplinary calendar reconstruction in náhuatl (‘centro de Puebla’ variant) according with his own nahua cosmosvision; and relying on Ochoa's correlation and on Tena's presuppositions as well. His proposal was translated to Spanish and English, and codified as an academic webpage in 2023.

Unfortunately, both Ochoa and Medina correlations go against strong evidence pointed out by scholars about the Mexica start of day and of the lack of a leap day in all Mesoamerican calendars. In this regard, some Mexican groups such as Kaltonak, are proposing a reconstruction of the calendar based on astronomical, archaeological and historical evidence.