シウポワリ

Also known as xiuhpohualli

The xiuhpōhualli (, from (“year”) + (“count”)) 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," which through Spanish usage came to be known as (“scores, groups of twenty”), with an inauspicious, separate 5-day period at the end of the year called the . The name given to the 20-day periods in pre-Columbian times is unknown, and though the Nahuatl word for moon or month, , is sometimes used today to describe them, the sixteenth-century missionary and ethnographer, Diego Durán explained that: