Archaeologists in Scotland have uncovered what is believed to be the world's oldest lunar calendar.
Twelve pits, said to have been created by hunter gatherers almost 10,000 years ago, were unearthed in a field at Crathes Castle, Aberdeenshire.
The pits are arranged in a 50-metre long row and are said to represent the months of the year and the phases of the moon.
Variation in the depths of the pits suggests that each pit or month may have also been divided into three roughly ten-day 'weeks' used to indicate the waxing moon, the gibbous/full moon and the waning moon.
The discovery of the Mesolithic 'calendar' overtakes a 5,000-year-old monument from Bronze Age Mesopotamia to claim the title of the world's oldest 'calendar'.
The site at Crathes Castle was originally excavated in 2004, but the findings were only analysed over the last six months using a purpose-built software.
Professor Vince Gafney led the archaeological project that discovered the structures.
'The evidence suggests that hunter-gatherer societies in Scotland had both the need and sophistication to track time across the years, to correct for seasonal drift of the lunar year and that this occurred nearly 5,000 years before the first formal calendars known in the Near East,' he said.
'In doing so, this illustrates one important step towards the formal construction of time and therefore history itself.'
Dr David Bates of the University of St Andrews said the discovery provided "exciting new evidence" of Mesolithic Scotland given it's age in comparison to other known calendars.
'This is the earliest example of such a structure and there is no known comparable site in Britain or Europe for several thousands of years after the monument at Warren Field was constructed.'
Scientists believe the Mesolithic monument discovered in Aberdeenshire was in use for some 4,000 years, from 8,000 BC to approximately 4,000 BC.