What did the Aztecs call their 365-day solar calendar?

The Aztecs called their 365-day solar calendar the xiuhpohualli, often written with a macron as xiuhpōhualli. The Nahuatl name means approximately “year count.” It organized the agricultural year and its associated religious festivals.

The xiuhpohualli consisted of 18 periods of 20 days, producing 360 named days, followed by five additional days called nemontemi. These final days were traditionally regarded as unfavorable or inauspicious. Spanish writers later called the 20-day periods veintenas, meaning “groups of twenty,” although the original pre-Columbian term for them is uncertain.

The solar calendar operated alongside the 260-day tonalpohualli, a ritual calendar used for divination and ceremonial timing. When the two cycles were combined, the same date returned only after 52 solar years, a period known as the Calendar Round. The New Fire ceremony marked the renewal of this cycle.

The xiuhpohualli is often confused with the famous Aztec Sun Stone. The stone contains calendrical imagery, but it is not itself the name of the 365-day calendar. Nor should the solar calendar be confused with the tonalpohualli, which had 260 days.