Mesoamerican Calendar System

Timeline

1. 1371–1374Tenochtitlan priestly academy · TenochtitlanThe sacred calendar combined 13 numbers with 20 day-name signs in a 260-day cycle, each day linked to a specific deity and auspicious or inauspicious attributes. In the 1370s priests used it to select auspicious days for sacrifices, marriages, campaigns, and coronations; day names were written on bark-paper books (amatl) and stone steles.
2. 1374–1378Agricultural zones of the Valley of Mexico · Valley of MexicoThe solar calendar divided the year into 18 months of 20 days plus 5 unlucky days (nemontemi), corresponding to the maize and bean growing cycles of the valley. In the 1370s each month had harvest, rain-god, and war-god festivals, and the ruler issued agricultural prohibitions and labor conscription orders according to the calendar.
3. 1378–1380Tenochtitlan central plaza and the Great Temple · TenochtitlanWhen the 260-day and 365-day cycles returned to their starting point together, a 52-year great cycle (xiuhmolpilli) was completed, requiring an extinguishing-of-fire—new-fire ceremony to renew the cosmic era. In the 1370s priests continuously observed stars and daytime shadows to correct the calendar, ensuring the accuracy of ceremonies and agricultural timing.