Mayans designed complex and accurate calendar

Uses Mayan mathematics
Far more complicated than simple leap years
Based on combined cycles of Sun, Moon, Venus.
Began in 3114 BC, a significant date in Mayan mythology.

Importance of Astonomy

In the Mesoamerican culture, the practice of astronomy was extremely important. To the Maya of Mesoamerica, this ancient science reflected order in the universe and the gods' place in it. This order reflected an inherent harmony present in their general theological view of the universe. To the Mayans, capturing the essence of time was of the utmost importance. In their cosmology, space and time were inevitably intertwined, as is evidenced by their complex calendar system that combines spatial attributes of the universe, such as animals and plants, with temporal movements of astronomical objects. Although the Mayans never invented water clocks or other specific time-keeping devices, they used the sky as a method of measuring the passage of time.

Mayan Astronomy

Mayan Astronomy

Although the Maya appreciated the sky as a whole and its infinite dimensions, they were particularly interested in certain specific astronomical objects. The sun, the moon, Venus, and specific star clusters and constellations were most important. These objects were given the most attention by the priest-astronomers, who spent generations finding the precise paths of these objects across the sky and through the seasons.

The most important object in the sky is the sun, which is universally recognized as the prime life-giver on Earth. Tonatiuh, a red eagle with a large and all-seeing eye, was the god associated with the sun. Because of the tilt of the Earth's axis, the sun appears at different positions in the sky depending on the time of year. This tilt is what produces the seasons experienced on Earth. The Maya accurately calculated times when the sun would rise and set, and even more amazing, they determined the length of the solar year to be 365 days. A tropical year is actually 365.2422 days long, so they were very close in their calculations. Unfortunately, even this small error means that the calendar which they created based on their solar year calculations would be off by approximately one month every 100 years, or by almost a whole six months every 600 years. This is obviously a dramatic difference, but there is evidence that the priest-astronomers continually updated their records and predictions so that the calendar remained accurate throughout the generations.