Stonehenge as viewed from the northeast.

Stonehenge as viewed from the northeast. (Image credit: Timothy Darvill)

An archaeologist now says that a solar calendar may have been used with each of the stones representing a day and a section of the circle of stones.

An accurate solar calendar is important for preventing the seasons from falling out of place, such as having winter during June. The Gregorian calendar uses a leap day every four years to account for a quarter of a day.

Archaeologists are confused about the purpose of the monument and how it would have been used over time, with a range of ideas being proposed such as a cemetery and a calendar.

Historians have seen the monumental composition of the evidence for a Neolithic calendar. Timothy Darvill, an archaeology professor at Bournemouth University in the U.K., wrote in the journal Antiquity that it was unclear how the calendar worked.

In photos, there is a walk through a monument.

The study of the meaning of numbers is what Darvill looked at to understand how the calendar worked. Some of the largesarsen stones that were linked together at the top are missing or have fallen over. 30 days would have been represented by these 30 stones. If you add this up, you get a total of 347 days.

Five pairs of stones may have represented five additional days because of the way the sarsen circle was arranged.

This diagram shows how the Stonehenge calendar may have worked. The 30 stones in the sarsen circle represent days which multiplied by 12 give 360. The five groups of stone in the middle represent five additional days giving 365 and the four station stones represent the need for a leap day every four years giving 365.25 days - a solar year.

This diagram shows how the Stonehenge calendar may have worked. (Image credit: Image courtesy Timothy Darvill)

There are four station stones that are outside the sarsen circle. The solar year could be created by adding a day to the calendar every four years.

Two of the stones in the circle, called S11 and S21, are thinner than the other stones and have a larger gap between them. The differences suggest that the people who built Stonehenge may have seen every 10th day as important.

It has been known for a long time that the winter and summer solstices are the same as the winter and summer sunrises. If the alignments occurred when they were supposed to, people could check to see if they were keeping track of time correctly.

Creation of calendar

Between 3000 B.C. and 2000 B.C., it was constructed. Between 2620 B.C. and 2480 B.C., the portions of Stonehenge that seem to form a calendar were constructed. This dating shows that the solar calendar was not built to be used at Stonehenge.

People were more interested in the phases of the moon when the first monument was built, and they became more interested in the solar calendar over time. It's hard to say why this change happened, writing hadn't yet spread to Britain. It is possible that religious beliefs changed to emphasize the sun and its movements.

The solar calendar is not certain how and why it was developed. He said that solar calendars were being developed in Mesopotamia and Egypt at the same time as Stonehenge was built. The idea of a solar calendar may have traveled to Britain through long-distance trade routes. It is possible that people in Britain developed the solar calendar without knowing about the developments in the Middle East.

The research was recently published and it is not known what reception it will get from other scholars.

It was originally published on Live Science.