The earliest known Mayan calendar has been found in an ancient house in Guatemala and it does not give any indication that the world is about to end, researchers say.
The findings were spotted in a small room in Mayan ruins in the rainforest at Xultun where royal scribes some 1,200 years ago apparently used walls as a blackboard to keep track of astronomical records and the society's intricate calendar.
The walls reveal the oldest known astronomical tables from the Maya - scientists already knew they must have been keeping such records at that time but, until now, the oldest known examples dated from about 600 years later.
Astronomical records were key to the Mayan calendar, which has gained attention recently because of doomsday warnings that predict the end of the world this December.
Experts say the new findings seem to contradict that prediction because the calculations include a time span longer than 6,000 years, meaning the calendar could extend well beyond 2012.
"Why would they go into those numbers if the world is going to come to an end this year?" said Anthony Aveni, of Colgate University in Hamilton, New York, an expert on Mayan astronomy.
"You could say a number that big at least suggests that time marches on."
Mr Aveni, along with William Saturno of Boston University and others, have reported the discovery in the latest issue of the journal Science .
Experts unconnected with the discovery said it was a significant advance.
"It's really a wonderful surprise," said Simon Martin, co-curator of an exhibit about the Mayan calendar at the University of Pennsylvania Museum of Archaeology and Anthropology.
He added while the results of the scribes' work were known from carvings on monuments, "we've never really been able to identify a working space, or how they actually went about things".