These notes pertain to the same Maya calendar that is sometimes erroneously thought to predict the world's end on or about December 22, 2012. The researchers who helped uncover and decipher the wall's inscriptions said the Maya calendar foresaw a vast progression of time, with the December 2012 date the beginning of a new calendar cycle called a baktun.

"They were looking at the way these cycles were turning," said William Saturno of Boston University, an author of an article on the find in the journal Science. "The Maya calendar is going to keep going and keep going for billions, trillions, octillions of years into the future, a huge number that we can't even wrap our heads around."

The faint numerical inscriptions on the wall in Guatemala measure out time in approximate six-month increments, based on six lunar cycles, with small stylized pictures of Maya gods to indicate which deity was the patron of a specific slice of time, the researchers said Thursday in an online briefing.

"It seems pretty clear that what we have here is a lunar calendar," said David Stuart of the University of Texas at Austin, another author of the Science article. The findings will also be published in the June issue of National Geographic, which funded some of the research.

The numbers on the wall were likely written by a scribe or calendar priest, who would have been an important figure in the Maya court, where monarchs were keenly interested in astronomy and sought to harmonize sacred rituals with events in the sky.

The wall was used the way a modern scientist might use a whiteboard, to write down frequently consulted formulas instead of having to look them up in a book, he said.

The fact that these calendar details were inscribed on the wall preserved them better than any book would have, since no books remain from the period when the inscriptions were made, probably around 800 AD, the researchers said.

In addition to the inscribed numbers, there were pictures on other walls of the structure, including an image of a king in a feather headdress, seated on a throne, with a white-garbed person peeking out from behind him. A painting of a scribe holding a stylus was on another wall.

These paintings were the first Maya art to be found on the walls of a house, the researchers said.

The structure, covered with vegetation, was detected in 2010 at the ruined Maya complex at Xultun in a rainforest area of Guatemala. Xultun, once home to tens of thousands of people, stretches over 12 square miles (31 square km), and thousands of the remaining structures have not yet been explored.

"It's weird that the Xultun finds exist at all," Saturno said in a statement. "Such writings and artwork on walls don't preserve well in the Maya lowlands, especially in a house buried only a meter below the surface."

(Reporting By Deborah Zabarenko; Editing by Eric Walsh)

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