Olympiad, << oh LIHM pee ad. >> In the Greek system of telling time, an Olympiad was the period of four years that elapsed between two successive celebrations of the Olympian, or Olympic, Games. This way of figuring time became common about 300 B.C. All events were dated from 776 B.C., the start of the first known Olympiad.
This method of counting time ceased about A.D. 440, after the 304th Olympiad. The Olympiads were used as measures of time by later Greek historians and other writers to refer to preceding centuries, but they were never in everyday use, as were months and years.
The beginning of the year of the Olympiad was determined by the first full moon after the summer solstice, the moment when the sun reaches its northernmost position in the sky. The first full moon after the solstice occurs about July 1.
See also Olympic Games (The ancient games).
