Tōnalpōhualli

Tonalpōhualli calendar representation

The basis of the tōnalpōhualli is unknown. Several theories have been advanced for this calendrical period: that it represents a Venusian cycle, that it represents the human gestation period, or that it represents the number of days between the zenithal passage of the sun in the tropical lowlands. On the other hand, some scholars including J. E. S. Thompson suggest that the tōnalpōhualli was not based on natural phenomena at all, but rather on the integers 13 and 20, both considered important numbers in Mesoamerica.

The other major Mexica calendar, the xiuhpōhualli, is a 365-day year, based on 18 months of 20 days and five nameless days. A xiuhpōhualli was designated by the name of its first tōnalpōhualli day. For example, Hernán Cortés met Moctezuma II on the day 8 Wind in the year 1 Reed (or November 8, 1519 in the Julian calendar[2]).

The xiuhpōhualli and the tōnalpōhualli would coincide approximately every 52 years.

Note that the symbols are arranged counterclockwise around the calendar stone.

• 
  Flower, Rain, Flint, Earthquake
• 
  Vulture, Eagle, Jaguar
• 
  Reed, Grass, Monkey, Dog
• 
  Water, Rabbit, Deer
• 
  Death, Snake, Lizard
• 
  House, Wind, Alligator

• Aztec calendar
• Aztec calendar stone
• Aztec mythology
• Maya calendar

• Discussion of origin of the 260-day cycle Archived 2008-05-30 at the Wayback Machine
• Animated tōnalpōhualli Archived 2010-02-12 at the Wayback Machine