Stonehenge was a solar calendar, says expert

The site was designed as a calendar and based on a solar year of 365.25 days.

02 March 2022

The Stonehenge monument served as an ancient solar calendar, according to research.

Professor Timothy Darvill concluded the site was designed as a calendar based on a solar year of 365.25 days, helping people keep track of the days, weeks and months.

His analysis includes new finds about the Wiltshire stone circle’s history, along with analysis of other ancient calendar systems.

“The clear solstitial alignment of Stonehenge has prompted people to suggest that the site included some kind of calendar since the antiquarian William Stukeley,” Prof Darvill said.

“Now, discoveries brought the issue into sharper focus and indicate the site was a calendar based on a tropical solar year of 365.25 days.”

Recent research showed 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. This indicates they worked as a single unit.

Prof Darvill, from Bournemouth University, 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 of the year that helped the inhabitants keep track of the days, weeks and months.

“The proposed calendar works in a very straightforward way. Each of the 30 stones in the sarsen circle represents a day within a month, itself divided into three weeks each of 10 days,” he said.

The distinctive stones in the circle mark the start of each week and the intercalary month of five days and a leap day every four years were also reflected in the design.

“The intercalary month, probably dedicated to the deities of the site, is represented by the five trilithons in the centre of the site,” Prof Darvill said.

“The four Station Stones outside the Sarsen Circle provide markers to notch up until a leap day.”

Stonehenge was designed as a solar calendar, suggesting the stones served as a physical representation of the year (Andrew Matthews/PA)
(Andrew Matthews/PA)

This means 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.

Such a calendar, with 10-day weeks and extra months, may seem unusual today but were adopted by many cultures during this period

“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 BC and was widely used at the start of the Old Kingdom about 2600 BC,” Prof Darvill said.

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

– The paper, Keeping time at Stonehenge, is published in the journal Antiquity.

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