Here’s what you’ll learn when you read this story:

• The Maya Calendar, first devised by the Olmecs and perfected by the ancient Maya civilization, is a complicated timekeeping system made up of three calendars.
• The Long Count Calendar covers a vast period of 5,125 years before resetting, and researchers recently found the oldest recording of this calendar in the Maya lowlands.
• Found at the ancient Maya site El Palmar on Stela 46, the start date of 8.7.1.0.0 works out to August 31, 180 C.E.—more than a century older than the previous earliest inscription.

While the Gregorian calendar is our best attempt at rendering Earth’s solar reality on paper, it’s far from the most complex calendrical system out there. That accolade belongs to the Maya calendar, which uses a system of three calendars—a 260-day divinatory calendar, a 365-day solar calendar, and a 5,125-year Long Count calendar—to track events through time.

Although the calendar system is best-known for its association with the Maya—a people who flourished in southern Mexico and northern Central America for thousands of years—its origins likely lie with the Olmecs, who predate the Maya civilization. Of the three calendars, it’s the Long Count calendar that gets the most attention, especially since its starting date of 4 Ajaw 8 Kumk'u (August 11, 3114 B.C.E.) helped German librarian Ernst Forstemann decode the whole system in the late 19^th century. Because the Long Count Calendar covers 13 b’ak’tun—a period of time that’s roughly 400 years—before resetting, conspiracy theories flourished around December 21, 2012, as that date marked the end of the final b’ak’tun (spoiler alert: nothing happened, and the calendar just reset).

Doomsday predictions aside, the Long Count calendar offers us a glimpse into ancient Maya society. By specifically marking historical events, it has helped scholars analyze Mayan artifacts such as stelae, which are upright stone monuments often engraved with depictions of ancient rulers. Now, in a new study published in the journal Ancient Mesoamerica, researchers from the U.S., Japan, and Mexico detail what they describe as the oldest Long Count date ever found in the Maya lowlands.

The date comes from the ancient Maya site of El Palmar in Campeche, Mexico, on Stela 46. The front of the stela depicts a ruler holding the head of a deity, likely the Jaguar god of the underworld. One side of the stela contains a Long Count number, and the other lateral side contains inscriptions of royal events. Maya Long Count entries contain five numbers derived from specific glyphs, and each number corresponds to a unit of time from the largest, b’ak’tun (400 years), to the smallest, k’in (one day). Calculating from the calendar’s start date, for example, July 4, 1776 would be translated as 12.8.0.1.13.

In the new study, Kenichiro Tsukamoto (from the University of California Davis) and his team calculated the date 8.7.1.0.0 on the lateral side of the stela, which translates to August 31, 180 C.E. If accurate, that would make Stela 46 the oldest Long Count entry in the Maya lowlands. It’s more than a century older than the next closest date, located on the Tikal Stela 29, which reads 8.12.14.15.0 (or July 8, 292 C.E.).

Reading the date wasn’t easy—Stela 46 was carved roughly 2,000 years ago, and two millennia of weather damage has steadily worn away the inscriptions. But by using photogrammetry and a high-resolution 3D scanner, the team was able to capture details at resolutions of just a tenth of a millimeter. Then, using software to artificially light the model from different angles, the researchers could eventually discern the worn-away hieroglyphics. The process isn’t perfect, and the team admits that other Long Counts—such as 8.7.0.5.0 or February 18, 180 C.E.— are possible. But regardless, the stela remains the oldest Long Count ever discovered.

“El Palmar Stela 46 and subsequent monuments suggest that the Long Count played a vital role in the continuity of kingship during the Classic period,” the authors wrote. “Further study of this region will provide new insights into the emergence of Maya kingship.”