The Aztec calendar is a system used by the Aztec civilization to track time and organize their agricultural and religious activities. It consists of two main cycles: the tonalpohualli, a 260-day ritual calendar, and the xiuhpohualli, a 365-day solar calendar. These cycles interlock to create a 52-year period known as a "Calendar Round." The calendar is often represented by a large stone disk, known as the Sun Stone, which features intricate carvings of various deities and symbols. The Aztecs believed that time was cyclical, and the calendar played a crucial role in their understanding of the universe and their place within it.