The Tonalpohualli is a 260-day calendar used by the ancient Mesoamerican cultures, particularly the Aztecs. It consists of 20 periods of 13 days, each associated with a specific symbol and deity. This calendar was essential for determining the timing of religious ceremonies, agricultural activities, and personal events. Each day in the Tonalpohualli has its own unique significance, influencing the lives of individuals and communities. People believed that the day they were born determined their personality and fate. The Tonalpohualli works alongside the Haab', a 365-day calendar, creating a complex system that guided the spiritual and daily lives of the Aztec civilization.