The Ancient Greek Olympics were held every 4 years. This 4-year period was known as an "Olympiad" and was used as a reference point for dating events. Since different Greek poleis (city-states) had their own dating system, the Olympiad provided a measure of uniformity. The Olympic games were named for the place they were held, Olympia, a district of Elis, in Southern Greece
All free Greek men were entitled to compete in the ancient Olympics. During the Roman Imperial period when Greece was part of the Roman Empire, the Olympic Games were more ecumenical.