The Xiuhpohualli (from xihuitl + pōhualli) 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 veintenas or mētztli (the contemporary Nahuatl word for month) with a separate 5-day period at the end of the year called the nemontemi.