An Olympiad (Greek: Ὀλυμπιάς, olympiás) is a period of four years associated with the Olympic Games of the Ancient Greeks. During the Hellenistic period, beginning with Ephorus, it was used as a calendar epoch.By this reckoning, the first Olympiad lasted from the summer of 776 BC to that of 772 BC.By extrapolation to the Gregorian calendar, the1st year of the 699th Olympiad begins in (Northern-Hemisphere) mid-summer 2017. A modern Olympiad refers to a four-year period beginning January 1 of a year in which the Summer Olympics are due to occur. The first modern Olympiad began in 1896, the second in 1900, and so on (the 31st began in 2016: see the Olympic Charter).

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