Washington, May 11 (IANS/EFE): A team of US archaeologists announced Thursday the discovery of the oldest Mayan calendar to date, a ninth-century artifact amid the ruins of an ancient city in Guatemala.

The calendar documents cycles of the moon and, apparently, those of Venus and Mars as well, Boston University's William Saturno and University of Texas archaeologist David Stuart told a press conference.

The find, to be detailed in this week's issue of the journal Science and the June issue of National Geographic, also further discredits the notion that the Mayas predicted the world would end in December 2012.

Proponents of the doomsday idea said 2012 would mark the conclusion of the last of the 13 "baktuns" - cycles of 400 years - that make up the Mayan calendar.

But the calendar found in Xultun, Guatemala, has 17 baktuns, and Stuart said the Mayas method of time measurement included units much larger than the baktun.

"The Mayan calendar is going to keep going for billions, trillions, octillions of years into the future," he said.

The hieroglyphs in Xultun are several hundred years older than the calendar and astronomical tables of the Dresden Codex, which dates from the 11th or 12th century.

The home containing the calendar was part of a large residential complex.

Though Xultun was discovered in 1915, 99.9 percent of the site has yet to be explored, according to Saturno, who spoke of "the great wealth of scientific material that remains in Guatemala in the Maya area for us to discover".