Archaeologists believe they have discovered the world's oldest lunar "calendar" in an Aberdeenshire field.
Excavations of a field at Crathes Castle found a series of 12 pits which appear to mimic the phases of the moon and track lunar months.
A team led by the University of Birmingham suggests the ancient monument was created by hunter-gatherers about 10,000 years ago.
The pit alignment, at Warren Field, was first excavated in 2004.
The experts who analysed the pits said they may have contained a wooden post.
The Mesolithic "calendar" is thousands of years older than previous known formal time-measuring monuments created in Mesopotamia.
The analysis has been published in the journal, Internet Archaeology.
The pit alignment also aligns on the Midwinter sunrise to provided the hunter-gatherers with an annual "astronomic correction" in order to better follow the passage of time and changing seasons.
Vince Gaffney, Professor of Landscape Archaeology at Birmingham, led the analysis project.
He said: "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.
"In doing so, this illustrates one important step towards the formal construction of time and therefore history itself."
The universities of St Andrews, Leicester and Bradford were also involved.