The Aztec calendar is the calendar

Calendar

A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. The name given to each day is known as a date. Periods in a calendar are usually, though not...

 system that was used by the Aztec

Aztec

The Aztec people were certain ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language and who dominated large parts of Mesoamerica in the 14th, 15th and 16th centuries, a period referred to as the late post-classic period in Mesoamerican chronology.Aztec is the...

s as well as other Pre-Columbian

Pre-Columbian

The pre-Columbian era incorporates all period subdivisions in the history and prehistory of the Americas before the appearance of significant European influences on the American continents, spanning the time of the original settlement in the Upper Paleolithic period to European colonization during...

 peoples of central Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

. It is one of the Mesoamerican calendars

Mesoamerican calendars

Mesoamerican calendars are the calendrical systems devised and used by the pre-Columbian cultures of Mesoamerica. In addition to the basic function of a calendar—defining and organizing periods of time in a way that allows events to be fixed, ordered and noted relative to each other and some...

, sharing the basic structure of calendars from throughout ancient Mesoamerica

Mesoamerica

Mesoamerica is a region and culture area in the Americas, extending approximately from central Mexico to Belize, Guatemala, El Salvador, Honduras, Nicaragua, and Costa Rica, within which a number of pre-Columbian societies flourished before the Spanish colonization of the Americas in the 15th and...

.

The calendar consisted of a 365-day calendar cycle called xiuhpohualli

Xiuhpohualli

The Xiuhpohualli was a 365-day calendar used by the Aztecs and other pre-Columbian Nahua peoples in central Mexico. It was composed of eighteen 20-day "months," called veintenas or metzli with a separate 5 day period at the end of the year called the nemontemi...

(year count) and a 260-day ritual cycle called tonalpohualli

Tonalpohualli

The tonalpohualli, a Nahuatl word meaning "count of days", is a 260-day sacred period in use in pre-Columbian Mesoamerica, especially among the Aztecs. This calendrical period is neither solar nor lunar, but rather consists of 20 trecena, or 13-day periods...

(day count). These two cycles together formed a 52-year "century," sometimes called the "calendar round

Calendar round

In the Mesoamerican calendars, calendar round dates are composed by interlacing the dates of a 260-day period with dates from a 365-day period...

".