Top image: The complex Mesoamerican calendars have fascinated for centuries. New LiDar surveys provide evidence that they were used much earlier than previously thought.

Renowned for their precision, vision, and place in time, Mesoamerican calendars have long been held up as an example of the early advancement of the civilizations of the indigenous people of North, South, and Central America. A new study has found that some of the great Mesoamerican peoples and cultures, the Maya and the Olmecs for example, were using the calendar over 3,000 years ago, around 1100 BC, several centuries earlier than previously thought.

The new study, published in the latest edition of the journal Science Advances , focused on the most famous 260-day cholq’ij (order of the days) calendar, used by these cultures along Mexico’s southern Gulf Coast as early as 3,100 years ago. Star-aligned ceremonial centers were built to keep track on this shorter calendar, with the oldest written evidence of this calendar earlier found on painted plaster mural fragments from a Maya site in Guatemala, between 300 and 200 BC.

The scientists employed the use of aerial surveys using LiDAR (Light Detection and Ranging) technology over an area of 32,641 square miles (84,516 square kilometers). In addition, these orientations were studied on a Digital Elevation Model (DEM), which was derived from the LiDAR. These were processed using ArcGIS software and other kinds of visualizations that crunch LiDAR data to create high resolution images of the earth’s surface, even bypassing dense vegetation like that of the Amazon rainforest .

The large Maya complex of Aguada Fénix near Tabasco, Mexico is covered in vegetation that LiDar can penetrate

The 260 Day Calendar: A Feat of Human Excellence

These surveys revealed something fascinating – over a hundred architectural complexes were aligned to facilitate timed observations of the rising and setting sun, moon, and other celestial objects, in line with the 260-day calendar.

This calendar has no months, but rather, twenty glyphs and signs, including crocodile, water, deer, grass, and eagle, combined with the numbers 1-13. The combination of both creates 260 days. It remains in use in most parts of Mesoamerica even today.

“It is obvious that the orientations reflect a complex worldview in which astronomical knowledge conditioned by practical concerns was intertwined with religious concepts,” says co-author Ivan Šprajc, who studies Mesoamerican archaeology and archaeoastronomy at the Slovenian Academy of Sciences and Arts.

The calendar did not just serve the purpose of recording time and structuring the changing seasons. The Jerusalem Post reports that the same calendar held a key role in Mesoamerican society, associated with important rituals and religious cosmology , and even anointing the next generation of children.

Existing knowledge has demonstrated that the Maya diligently studied the sun and moon, planets, the Milky Way, and other astronomical phenomena. This included the length of the synodic month, and calculating the length of the tropical solar year . The use of 260 days remains unclear, though various theories suggest that the numbers 13 and 20 were important to the people.

Lidar-based images of two sites with similar spatial plans, each with 20 edge platforms. (A) San Lorenzo. (B) Aguada Fénix. The sites align with celestial objects using the Maya 260 day calendar.

Orientation and Adjoining Structures: Studying the Ceremonial Complexes

What the data has provided is 415 distinct ceremonial complexes of note (from more than a whopping 33,000) dating from 1100 BC to 250 AD. These include the Olmec center of San Lorenzo , Mexico, and the recently discovered Aguada Fénix on a Mexican ranch located near the border of Guatemala, which may be the biggest and oldest known Maya monumental complex, reported The Smithsonian .

LiDar studies of Aguada Fénix reveal what is currently the largest and oldest known Maya monument complex.

For the purposes of the study, the site’s astronomical orientations on notable days of the 260-day calendar were analyzed, including the lunar cycles and the two solstices. The most commonly occurring orientations were dated between 1100 and 750 BC, and aligned with sunrises on February 11 and October 29, when juxtaposed against the Gregorian calendar . These two dates on the cholq’ij were separated end to end by the full 260 days. The presence of Venus’ star coinciding with the rainy season was another such observation.

 “Since the early orientations that we have analyzed [that] reflect the use of this cycle are embedded in the architectural complexes located along the southern Gulf Coast, this was most likely the area where the 260-day count originated,” says Šprajc.

The new study’s greatest strength lies in its large sample size, supporting other written evidence that timekeeping arose during the Formative period (1000 BC – 500 AD). All in all, the biggest takeaway is clinching evidence that the Maya calendar had its origins much before the actual written one was evidenced.

Other cosmological alignments and their specific orientations remain undeciphered for the moment, but going forward, these discoveries raise further questions about the practices of the ancient Mesoamerican tribes. These structures also lie at the core of community building and Maya identity, opening up even more possibilities!