Daily Times

No one is entirely sure why, or even how, the mighty Stonehenge was built around 5,000 years ago.

Now, a new study argues the world-famous Wilshire monument served as an ancient solar calendar, helping people track the days of the year.

Professor Timothy Darvill, an archaeologist at Bournemouth University, has analysed the numbers and positioning of Stonehenge’s great sandstone slabs, called sarsens.

Sarsens form all 15 stones of Stonehenge’s central horseshoe, the uprights and lintels of the outer circle, as well as outlying stones such as the Heel Stone, the Slaughter Stone and the Station Stones. Stonehenge, Professor Darvill says, was a ‘simple and elegant’ perpetual calendar based on a tropical solar year of 365.25 days.

He says the entire site was the physical representation of one month – and that the 30 stones in the sarsen circle each represented one day within the month.

It’s thought that people at Stonehenge simply marked the days of the month each represented by a stone, perhaps using a small stone or a wooden peg.

Although no one can be certain why Stonehenge was built, a school of thought that it served as an ancient calendar has long existed.

Other theories include that it was a cult centre for healing, a temple, a place where ancestors were worshipped or even a graveyard.

‘Stonehenge has long been thought to incorporate some kind of calendar, although its specific purpose and exactly how it worked remain far from clear,’ says Professor Darvill in his paper.

‘Understanding the sarsen elements as a unified group and recognising the numerical significance of the elements in each component opens up the possibility that they represent the building blocks of a simple and elegant perpetual calendar based on the 365.25 solar days in a mean tropical year.’

It’s already known that the whole layout of Stonehenge is positioned in relation to the solstices, or the extreme limits of the sun’s movement.

English Heritage explains: ‘At Stonehenge on the summer solstice, the sun rises behind the Heel Stone in the north-east part of the horizon and its first rays shine into the heart of Stonehenge.

‘Observers at Stonehenge at the winter solstice, standing in the enclosure entrance and facing the centre of the stones, can watch the sun set in the south-west part of the horizon.’

With this new study, it seems like dwellers at the famous henge not only used to track times of the year, but days of the month too.

‘What they did I think was simply to mark the days represented by the stone,’ Professor Darvill told MailOnline.

‘We have some later prehistoric calendars where they list the days and have a hole next to each so they could mark them with a peg.

‘I think something similar would have happened at Stonehenge, perhaps using a small stone or a wooden peg.’

Recent research had shown that Stonehenge’s sarsens were added during the same phase of construction – around 2500 BC. They were sourced from the same area and subsequently remained in the same formation – indicating they worked as a single unit. As such, Professor Darvill analysed these stones, examining their numerology and comparing them to other known calendars from this period.

He identified a solar calendar in their layout, suggesting they served as a physical representation to allow the ancient inhabitants of Wiltshire keep track of the days. When Stonehenge was built, one month consisted of three weeks. Each of these weeks consisted of 10 days.

Professor Darvill said there are distinctive stones in the circle that mark the start of each of these three weeks in the month. The 10-day week was a key part of the Egyptian civil calendar from about 2600 BC, he added.

‘Such a solar calendar was developed in the eastern Mediterranean in the centuries after 3000 BC and was adopted in Egypt as the Civil Calendar around 2700 and was widely used at the start of the Old Kingdom about 2600 BC.’

This raises the possibility that the calendar tracked by Stonehenge may stem from the influence of one of these other cultures.

Nearby finds hint at such cultural connections – the nearby Amesbury archer, buried nearby around the same period, was born in the Alps and moved to Britain as a teenager.

Additionally, an intercalary month of five days and a leap day every four years were needed to match the solar year.

‘The intercalary month, probably dedicated to the deities of the site, is represented by the five trilithons in the centre of the site,’ said Professor Darvill.

‘The four Station Stones outside the Sarsen Circle provide markers to notch-up until a leap day.’

As such, the winter and summer solstices would be framed by the same pairs of stones every year.

One of the trilithons also frames the winter solstice, indicating it may have been the new year.

This solstitial alignment also helps calibrate the calendar – any errors in counting the days would be easily detectable as the sun would be in the wrong place on the solstices.

According to Professor Darvill, the identification of a solar calendar at Stonehenge should transform how we see it. ‘Finding a solar calendar represented in the architecture of Stonehenge opens up a whole new way of seeing the monument as a place for the living,’ he said.

‘A place where the timing of ceremonies and festivals was connected to the very fabric of the universe and celestial movements in the heavens.’

The study has been published today in the journal Antiquity.