Nahua peoples
The Xiuhpōhualli (, from + ) is a 365-day calendar used by the Aztecs and other pre-Columbian Nahua peoples in central Mexico. It is composed of eighteen 20-day "months," called or (the contemporary Nahuatl word for month) with a separate 5-day period at the end of the year called the . Whatever name that was used for these periods in pre-Columbian times is unknown. Through Spanish usage, the 20-day period of the Aztec calendar has become commonly known as a . The Aztec word for moon is , and this word is today to describe these 20-day periods, although as the sixteenth-century missionary and early ethnographer, Diego Durán explained: