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Aztec Dates from Codex Mendoza

Aztec calendrical dates using pictograms and dots

Folio 5v from the Codex Mendoza (a history of Aztec rulers, conquests and daily life compiled around 1541) depicts conquests by Itzcōhuātl, fourth king of the Aztec capital Tenochtitlan. The vertical column on the left of this page shows years in the Aztec sacred almanac calendrical system, which consisted of pictograms representing day signs plus number coefficients that cycled in a fixed order depicted using an arrangements of dots.

Aztec Dates from Codex Mendoza

The Aztec sacred calendar was constructed using a sequence of 20 day names paired with year numbers running sequentially from 1 to 13. In folio 5v from the Codex Mendoza, a vertical column of years is shown with the dates running from top to bottom as 1 Flint, 2 House, 3 Rabbit, 4 Reed, down through 13 Flint. The years express the reign of Itzcōhuātl, fourth ruler of Tenochtitlan, who is depicted as the seated figure and ruled from 1 Flint (1428 CE) to 13 Flint (1440 CE). As can be seen, the year-number dots are arranged in groups of five with the exception of 11 Rabbit.

Artifact dimensions

22.7 cm × 31.0 cm (71 pages; European paper)

Artifact origin


Catalog number

fol. 005 v, Bodleian Library MS. Arch. Selden. A. 1


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Computational Explanation

Additional Reading

  • Berdan, F. and Anawalt, P. R. The Essential Codex Mendoza. Berkeley, CA: University of California Press, 1997.
  • Bernal, I. and León-Portilla, M. Plate 5 in Historia de México, Vol. 2. Barcelona, Spain: Salvat Editores, p. 296, 1974.
  • Pappas, T. The Joy of Mathematics: Discovering Mathematics All Around You. San Carlos, CA: Wide World Publishing/Tetra, pp. 128–129, 1989.
  • Payne, S. E. and Closs, M. P. "A Survey of Aztec Numbers and Their Uses." Ch. 8 in Native American Mathematics (Ed. M. P. Closs). Austin, TX: University of Texas Press, pp. 213–235, 1996.

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