The Aztec or Mexica calendar is the calendrical system used by the Aztecs as well as other Pre-Columbianpeoples of central Mexico. It is one of the Mesoamerican calendars, sharing the basic structure of calendars from throughout ancient Mesoamerica. The Aztec sun stone, also called the calendar stone, is on display at the National Museum of Anthropology in Mexico City. The calendar consisted of a 365-day calendar cycle called xiuhpōhualli and a 260-day ritual cycle called tōnalpōhualli. These two cycles together formed a 52-year "century", sometimes called the "calendar round". The xiuhpōhualli is considered to be the agricultural calendar, since it is based on the sun, and the tōnalpōhualli is considered to be the sacred calendar.
Tōnalpōhualli
The tōnalpōhualli 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 which the cycle of numbers would restart 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 for the two cycles to realign and repeat the sequence back on 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 also bears 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 also 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 because they believed that 52 years was a life cycle and at the end of any given life cycle the gods could take away all that they have and destroy the world.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 "thirteen". The original Nahuatl term is not known. 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:
Trecena
Deity
Trecena
Deity
1 Crocodile
Ōmeteōtl
1 Monkey
Patecatl
1 Jaguar
Quetzalcoatl
1 Lizard
Itztlacoliuhqui
1 Deer
Tepēyōllōtl
1 Quake
Tlazōlteōtl
1 Flower
Huēhuecoyōtl
1 Dog
Xipe Totec
1 Reed
Chalchiuhtlicue
1 House
Ītzpāpālōtl
1 Death
Tōnatiuh
1 Vulture
Xolotl
1 Rain
Tlāloc
1 Water
Chalchiuhtotolin
1 Grass
Mayahuel
1 Wind
Chantico
1 Snake
Xiuhtecuhtli
1 Eagle
Xōchiquetzal
1 Flint
Mictlāntēcutli
1 Rabbit
Xiuhtecuhtli
is the Aztec year count. One year consists of 360 named days and 5 nameless. 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 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 believed to be more 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.
The ancient Mexicans counted their years by means of four signs combined with thirteen numbers, obtaining periods of 52 years, which are commonly known as Xiuhmolpilli, a popular but incorrect name; the correct Nahuatl word for this cycle is Xiuhnelpilli. We can see below the table with the current years:
Tlalpilli Tochtli
Tlalpilli Acatl
Tlalpilli Tecpatl
Tlalpilli Calli
1 tochtli / 1974
1 acatl / 1987
1 tecpatl / 2000
1 calli / 2013
2 acatl / 1975
2 tecpatl / 1988
2 calli / 2001
2 tochtli / 2014
3 tecpatl / 1976
3 calli / 1989
3 tochtli / 2002
3 acatl / 2015
4 calli / 1977
4 tochtli / 1990
4 acatl / 2003
4 tecpatl / 2016
5 tochtli / 1978
5 acatl / 1991
5 tecpatl / 2004
5 calli / 2017
6 acatl / 1979
6 tecpatl / 1992
6 calli / 2005
6 tochtli / 2018
7 tecpatl / 1980
7 calli / 1993
7 tochtli / 2006
7 acatl / 2019
8 calli / 1981
8 tochtli / 1994
8 acatl / 2007
8 tecpatl / 2020
9 tochtli / 1982
9 acatl / 1995
9 tecpatl / 2008
9 calli / 2021
10 acatl / 1983
10 tecpatl / 1996
10 calli / 2009
10 tochtli / 2022
11 tecpatl / 1984
11 calli / 1997
11 tochtli / 2010
11 acatl / 2023
12 calli / 1985
12 tochtli / 1998
12 acatl / 2011
12 tecpatl / 2024
13 tochtli / 1986
13 acatl / 1999
13 tecpatl / 2012
13 calli / 2025
Reconstruction of the Solar calendar
For many centuries scholars had tried to reconstruct the Calendar. The latest and more accepted 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 confirms 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 verified 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. Due to the inaccuracies of relying on post-conquest sources, Ruben Ochoa used pre-columbian sources to reconstruct the calendar. To date his calendar correlation is the most accurate as a result.
