The Aztec calendar was the calendar of the Aztec people of Pre-Columbian Mexico. It is one of the Mesoamerican calendars, sharing the basic structure of calendars from throughout ancient Mesoamerica.

The calendar consisted of a 365 day calendar cycle and a 260 day ritual cycle. These two cycles together formed a 52 year "century", sometimes called the "Calendar Round".

365 day calendar

The solar calendar of 365 days, called the Vague Year (or Civil Year), was composed of 18 months of 20 days each, with a period of 5 or 6 days added at the end. The 360-day period was called "xíhuitl" by Aztecs, . The final unlucky days were called "Nemontemi " in Nahuatl.

Each month had its own special name, and the days were numbered from zero to nineteen. The days of the last month, Nemontemi, were numbered from zero to four.

260 day cycle

This solar calendar was inseparable from the Sacred Round, or Sacred Almanac. The priests used this ritual calendar of 260 days called Tonalpohualli primarily for divinatory purposes.

The method of naming the individual days consisted in the combination of twenty pictorial signs with the numbers one to thirteen.

Each of the day signs also association with one of the four cardinal directions.

The 20 day signs are:

Cipactli (alligator, aquatic monster) (East)

Éhecatl (wind, wind god) (North)

Calli (house) (West}

Cuetzpalin (lizard){South}

Cóatl (serpent, snake)(E)

Miquiztli (death)(N)

Mázatl (deer)(W)

Tochtli (rabbit) (S)

Atl (water)(E)

Itzcuintli (dog)(N)

Ozomatli (monkey)(W)

Malinalli (dead grass) (S)

Ácatl (reed)(E)

Océlotl (ocelot, jaguar)(N)

Quauhtli (eagle)(W)

Cozcaquauhtli (king buzzard , vulture) (South)

Ollin (motion, earthquake)(East)

Técpatl (flint, flint knife)(North)

Quiáhuitl (rain)(West)

Xóchitl (flower)(South)

These day signs would be combined with numbers, for example: 1 Cipactli, 2 Eecatl, 3 Calli, and so on to 13 Acatle, which was followed by 1 Ocelotl, 2 Quauhtli, etc. There being no common factor to the numbers 13 and 20, a period of 13 x 20 days, or 260, would elapse before the sign 1 Cipactli would recur. This period of 260 days constituted the divinatory or ritual calendar , known as tonalamatl . The tonalamatl was subdivided in various ways; in some manuscripts each of the twenty 13-day periods, or weeks, is shown separately, together with the figure of a god who was especially associated with the first day, but whose influence was supposed to extend over the whole "week". In some manuscripts the tonalamatl is arranged on a different system: in five long horizontal rows of 52 days each. Each row, and each vertical column of five days, is provided with a presiding deity symbol, the influence of which must be assessed.

See also: Maya calendar

External links:

http://www.azteccalendar.com/

Aztec Calendar: Math and Design Earth/matriX: Science in Ancient Artwork by Charles William Johnson