Professor Timothy Darvill from Bournemouth University says Stonehenge functioned as an ancient solar calendar, based on a tropical solar year of 365.25 days. The site helped people keep track of the days, weeks, and months.
Recent research has revealed that Stonehenge’s sarsen stones were added around 2500 BC. Professor Darvill analysed the stones, investigating their numerology and comparing them to other known calendars from the period.
A physical representation of the year
He discovered a solar calendar in their layout, indicating that they functioned as a physical representation of the year. The distinctive stones in the circle mark the start of each week. Professor Darvill said:
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.
Also reflected in the design is an intercalary month of five days and a leap day every four years. In addition, the same pairs of stones frame the winter and summer solstices every year.
This solstitial alignment would prevent any errors in counting the days, as the sun would be in the wrong place on the solstices.
Was Stonehenge's calendar influenced by other cultures?
A calendar with 10-day weeks and extra months may seem odd today but were used by many cultures during this period. Professor Darvill said:
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.
This means that Stonehenge's calendar may possibly be influenced by one of these other cultures.