Aztec calendar

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The Aztec sun stone and a depiction of its base

The Aztec or Mexica calendar is the calendrical system used by the Aztecs as well as other Pre-Columbian peoples of central Mexico. It is one of the Mesoamerican calendars, sharing the basic structure of calendars from throughout ancient Mesoamerica.

The Aztec sun stone depicts calendrical symbols on its inner ring.

The Aztec sun stone, also called the calendar stone, is on display at the National Museum of Anthropology in Mexico City. The calendar consists of a 365-day calendar cycle called xiuhpōhualli (year count) and a 260-day ritual cycle called tōnalpōhualli (day count). These two cycles together form 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 ("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 which 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 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.

Image Nahuatl name Pronunciation English translation Direction Cipactli [siˈpáktɬi] Crocodile Alligator Caiman Crocodilian Monster Dragon East Ehēcatl [eʔˈéːkatɬ] Wind North Calli [ˈkálːi] House West Cuetzpalin [kʷetsˈpálin̥] Lizard South Cōātl [ˈkóːwaːtɬ] Serpent Snake East Miquiztli [miˈkístɬi] Death North Mazātl [ˈmásaːtɬ] Deer Animal West Tōchtli [ˈtóːtʃtɬi] Rabbit South Ātl [ˈaːtɬ] Water East Itzcuīntli [itsˈkʷíːn̥tɬi] Dog North

Image Nahuatl name Pronunciation English translation Direction Ozomahtli [osoˈmáʔtɬi] Monkey West Malīnalli [maliːˈnálːi] Grass South Ācatl [ˈáːkatɬ] Reed East Ocēlōtl [oːˈséːloːtɬ] Ocelot Jaguar North Cuāuhtli [ˈkʷáːʍtɬi] Eagle West Cōzcacuāuhtli [koːskaˈkʷáːʍtɬi] Vulture South Ōlīn [ˈoːliːn̥] Movement Quake Earthquake East Tecpatl [ˈtékpatɬ] Flint Flint Knife North Quiyahuitl [kiˈjáwitɬ] Rain West Xōchitl [ˈʃoːtʃitɬ] Flower South

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.

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 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:

Xiuhpōhualli

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.

#	Durán time	Sahagún time	Fiesta names	Symbol	English translation
1	Mar 1 – Mar 20	Feb 2 – Feb 21	Atlcahualo, Cuauhitlehua		Ceasing of Water, Rising Trees
2	Mar 21 – Apr 9	Feb 22 – Mar 13	Tlacaxipehualiztli		Rites of Fertility; Xipe-Totec ("the flayed one")
3	Apr 10 – Apr 29	Mar 14 – Apr 2	Tozoztontli		Lesser Perforation
4	Apr 30 – May 19	Apr 3 – Apr 22	Huey Tozoztli		Greater Perforation
5	May 20 – Jun 8	Apr 23 – May 12	Tōxcatl		Dryness
6	Jun 9 – Jun 28	May 13 – Jun 1	Etzalcualiztli		Eating Maize and Beans
7	Jun 29 – July 18	Jun 2 – Jun 21	Tecuilhuitontli		Lesser Feast for the Revered Ones
8	July 19 – Aug 7	Jun 22 – Jul 11	Huey Tecuilhuitl		Greater Feast for the Revered Ones
9	Aug 8 – Aug 27	Jul 12 – Jul 31	Tlaxochimaco, Miccailhuitontli		Bestowal or Birth of Flowers, Feast to the Revered Deceased
10	Aug 28 – Sep 16	Aug 1 – Aug 20	Xócotl huetzi, Huey Miccailhuitl		Feast to the Greatly Revered Deceased
11	Sept 17 – Oct 6	Aug 21 – Sept 9	Ochpaniztli		Sweeping and Cleaning
12	Oct 7 – Oct 26	Sept 10 – Sept 29	Teotleco		Return of the Gods
13	Oct 27 – Nov 15	Sept 30 – Oct 19	Tepeilhuitl		Feast for the Mountains
14	Nov 16 – Dec 5	Oct 20 – Nov 8	Quecholli		Precious Feather
15	Dec 6 – Dec 25	Nov 9 – Nov 28	Pānquetzaliztli		Raising the Banners
16	Dec 26 – Jan 14	Nov 29 – Dec 18	Atemoztli		Descent of the Water
17	Jan 15 – Feb 3	Dec 19 – Jan 7	Tititl		Stretching for Growth
18	Feb 4 – Feb 23	Jan 8 – Jan 27	Izcalli		Encouragement for the Land & People
18u	Feb 24 – Feb 28	Jan 28 – Feb 1	nēmontēmi (5 day period)		Empty days (no specific activities or holidays)

Xiuhmolpilli

The ancient Mexicans 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 Solar calendar

For many centuries scholars had tried to reconstruct the Calendar. A widely 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 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.

In this regard, 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 precisely on Ochoa’s smart correlation and on Tena’s presuppositions as well.  His proposal was translated to Spanish and English, and codified as an academic webpage in 2023.

See also

• Maya calendar
• Mesoamerican calendars
• Aztec New Year
• Muisca calendar