The xiuhpohualli is the Aztec calendar that consists of 365 days, divided into 18 months of 20 days each, plus an additional 5 "empty" days. Each month is associated with specific festivals and rituals, reflecting the agricultural and religious practices of the Aztec civilization. This calendar is part of a larger system that includes the tonalpohualli, a 260-day ritual calendar. Together, these calendars were used to track time, plan agricultural activities, and schedule religious ceremonies, playing a crucial role in the daily life of the Aztecs.