The Maya are famous for their complex, intertwined calendric systems, and now one calendar, the Maya Long Count, is empirically calibrated to the modern European calendar, according to an international team of researchers.

"The Long Count calendar fell into disuse before European contact in the Maya area," said Douglas J. Kennett, professor of environmental archaeology, Penn State.

"Methods of tying the Long Count to the modern European calendar used known historical and astronomical events, but when looking at how climate affects the rise and fall of the Maya, I began to question how accurately the two calendars correlated using those methods."...