The ancient civilization known for its calendar and astronomical knowledge is the Maya. Flourishing in Mesoamerica from around 2000 BCE to the Spanish conquest in the 16th century, the Maya developed complex calendars based on a deep understanding of celestial movements. Their most famous calendars include the Tzolk'in (260-day) and the Haab' (365-day), which were intricately linked to their agricultural cycles and religious practices. The Mayans also made significant advances in mathematics, including the use of the concept of zero, and showcased their astronomical expertise in impressive structures like observatories. Their cultural legacy includes sophisticated art, architecture, and writing systems.