A trecena is a 13-day period used in pre-Columbian Mesoamerican calendars. The 260-day calendar (the tonalpohualli) was divided into 20 trecenas. Trecena is derived from the Spanish chroniclers and translates to “a group of thirteen” in the same way that a dozen (or in Spanish docena) relates to the number twelve. It is associated with the Aztecs, but is called different names in the calendars of the Maya, Zapotec, Mixtec, and others of the region.
Many surviving Mesoamerican codices, such as Codex Borbonicus, are divinitory calendars, based on the 260-day year, with each page representing one trecena.
| n.º | Trecena | Aztec deities associated | Cardinal point |
|---|---|---|---|
| 1 | 1 Cipactli (Caiman or aquatic monster) | Tonacatecuhtli | East |
| 2 | 1 Ehecatl (Wind) | Quetzalcoatl | North |
| 3 | 1 Calli (House) | Tepeyollotl, Quetzalcoatl | West |
| 4 | 1 Cuetzpallin (Lizard) | Huehuecoyotl or Macuilxochitl | South |
| 5 | 1 Coatl (Snake) | Chalchiuhtlicue and Tlazolteotl | East |
| 6 | 1 Miquiztli (Death) | Tonatiuh and Tecuciztecatl | North |
| 7 | 1 Mazatl (Deer) | Tlaloc and Chicomecoatl o 4 Ehécatl | West |
| 8 | 1 Tochtli (Rabbit) | Mayahuel and Xochipilli or Cinteotl | South |
| 9 | 1 Atl (Water) | Tlahuizcalpantecuhtli or Xiuhtecuhtli | East |
| 10 | 1 Itzcuintli (Dog) | Mictlantecuhtli | North |
| 11 | 1 Ozomatli (Monkey) | Patecatl and Cuauhtliocelotl | West |
| 12 | 1 Malinalli (Grass) | Itztlacoliuhqui | South |
| 13 | 1 Acatl (Reed) | Tezcatlipoca or Uactli and Ixcuina or Tlazolteotl | East |
| 14 | 1 Ocelotl (Ocelot or Jaguar) | Tlazolteotl | North |
| 15 | 1 Cuauhtlil (Eagle) | Xipe Totec and Quetzalcoatl | West |
| 16 | 1 Cozcacuauhtli (Vulture) | Itzpapalotl | South |
| 17 | 1 Ollin (Movement or Earthquake) | Xolotl and Tlalchitonatiuh or 4 Ollin | East |
| 18 | 1 Tecpatl (Flint or Knife) | Chalchiuhtotolin | North |
| 19 | 1 Quiahuit (Rain) | Tonatiuh | West |
| 20 | 1 Xochitl (Flower) | Xochiquetzal and Tezcatlipoca | South |