The ancient civilization most notably associated with the development of the calendar is the Mayan civilization. The Maya created an intricate calendar system that included a 260-day religious calendar called the Tzolk'in and a 365-day solar calendar known as the Haab'. Their calendar was remarkable for its precision and was used to schedule agricultural and ceremonial events. The Mayans also developed the Long Count calendar, which allowed them to track longer durations of time. This sophisticated understanding of celestial movements and timekeeping significantly impacted their culture, activities, and governance, showcasing their advanced astronomical and mathematical knowledge.