Researchers have now solved how Mayans used their 819-day calendar

It really needed a broad view to be fully understood.
Ameya Paleja
Stock image representing ancient Mayan works
Image representing ancient Mayan works


Researchers at Tulane University in Louisiana have solved the mystery of the 819-day calendar used by ancient Mayans. Using a 45-year span, the researchers were able to match the planetary cycles of all planets that might have been visible to astronomers of the civilization.

Research on ancient Mayan civilization has thrown up multiple calendars that were likely used by scholars of the time, but not all of them make sense in today's world. One such calendar was discovered in the glyphic texts – the native writing system of the Mayans and had researchers wondering about its purpose.

How was an 819-day calendar used?

For a civilization that is used to a 365-day calendar, it is difficult to make sense of a calendar that has 819 days, especially since the revolution of our own planet is nowhere close to this number.

Moreover, ancient glyphs have shown the calendar to consist of four parts and even boast a color-directional scheme, making the mystery even more intriguing. However, researchers John Linden and Victoria Bricker have cracked the purpose of the calendar by simply broadening their point of view.

Instead of looking at the calendar over short periods of time, they used it for over 20 periods of 819 days each and found a pattern that emerged with regard to the synodic period of planets. A synodic period is the time interval taken by a planet to visually appear at the same location in the sky when seen from Earth.

Researchers have now solved how Mayans used their 819-day calendar
Pictorial representation of various planets visible from Earth

Twenty counts of the 819-day period are 16,380 days or roughly 45 years. Looking at planets in the sky, one finds that the 819-day period perfectly matches the synodic period of Mercury, which is 117 days.

Moving further, the researchers found that Mars, with a synodic period of 780 days, exactly matches 20 cycles of an 819-day calendar, while Venus needs seven synodic periods to match five counts of 819. Going further, Jupiter takes 39 periods and matches 19 counts of 819, while Saturn has 13 periods in six 819-day counts.

The researchers state that instead of limiting their focus to just one or two planets, ancient Mayans created a large calendar system that could be used to predict the synod periods of all visible planets.

It might sound like a bit complex math was all that was needed to figure this out, but for the ancient Mayans, it was a lot of observation that went in first before a calendar could be made.

The research findings were published in the journal Ancient Mesoamerica.


Arguably the most enigmatic of the Maya calendar cycles, the 819-day count has challenged modern scholars for decades. Even today it is not completely explained and there are several areas for further research, including its relationship with the synodic periods of the planets visible to the naked eye. Earlier research has demonstrated a four-part, color-directional scheme for the 819-day count such that each of the calendar stations progress in increments of 819 days in cycles of 4 × 819 days. Although prior research has sought to show planetary connections for the 819-day count, its four-part, color-directional scheme is too short to fit well with the synodic periods of the visible planets. By increasing the calendar length to 20 periods of 819-days a pattern emerges in which the synodic periods of all the visible planets commensurate with station points in the larger 819-day calendar.

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