Stonehenge was designed as a solar calendar

A professor studying this ancient civilization is certain that their calendar year was incredibly similar to our modern-day one.

Scientists have long assumed that Stonehenge was designed as a calendar, although they did not know which one. It was believed there could have been sixteen months in this calendar, and it might have belonged to several civilizations. The scientific world is almost sure that the calendar corresponds to a tropical solar year, which lasts 365.25 days. A week had ten days; a month had four weeks. Every four years, another five days were added to their standard months – allowing the calendar to correlate with the sun.

The calendar was created approximately 2500 BC. The system that the calendar is based on can be traced back to five hundred years before the emergence of Stonehenge.