The oldest calendar known to exist was created some 5,000 years ago in Mesopotamia—but it's looking positively youthful in the face of a new find in northern Scotland. A dig at Warren Field in Aberdeenshire in 2004 is just now giving up its secrets, with archaeologists revealing that a series of 12 pits found there may in fact be the world's oldest calendar. They believe the Stone Age-era pits each acted as a stand-in for a calendar month, with the 12 collectively representing a year. Additionally, the pits may have collectively represented a single lunar month, and their varied depths in the 165-foot arc-shaped row indicate that time period was split into what the Independent calls three "weeks"—waxing, full, and waning.
The Australian calls out two notable aspects of the pits: For one, Scotland's prehistoric hunter-gatherer tribes have long been considered "civilization's late starters"; the find somewhat unravels that belief. Second, their calendar took into account "lunar drift"; because lunar months don't precisely align with the passage of a year, most early calendars tracked only the former. But these pits would have been able to reveal the arrival of the midwinter solstice and, with it, the year's end, a further indication of the people's sophistication. A neat side note from the BBC: The Warren Field site was identified as one worth investigating via odd crop marks seen from above by the country's Royal Commission on the Ancient and Historical Monuments.