Explore the sophisticated Aztec calendar system in this fascinating episode of The Aztec Gods. Host Edmund Cross reveals how the ancient Aztecs developed one of history's most complex timekeeping systems, combining the 260-day sacred Tonalpohualli with the 365-day solar Xiuhpohualli calendar. Discover the twenty sacred day signs, the role of Aztec priest-astronomers called tonalpouhque, and how the 52-year calendar round shaped every aspect of Aztec civilization. Learn about the cosmic significance of time in Aztec culture, from determining auspicious days for major life events to timing religious ceremonies and military campaigns. The episode examines archaeological evidence of Aztec astronomical knowledge, including temple alignments with celestial events and the mathematical precision of their calendar calculations. Cross discusses how the calendar system reflected Aztec beliefs about cyclical time, divine influence, and cosmic balance, requiring human participation through ritual to maintain harmony between earth and sky. The episode also touches on the enduring legacy of Aztec timekeeping among modern descendants in Mexico and ongoing archaeological research revealing new insights into this remarkable intellectual achievement of ancient Mesoamerican civilization.