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.
Every month had its name, and the days of the month were numbered from one to twenty. The days of the last month, Nemontemi, were numbered from one to five.The box at the top of the stone contains the stone's year of creation, in this case 1479 CE.
The solar calendar of 365 days 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 bears an association with one of the four cardinal directions.The 20 day signs are depicted in the calendar image to the right. They are arrayed in a circle surrounding the central face. .