Olympiad of the games are so scanty that historians are not certain whether after 261 they were still held every four years. During the early years of the Olympiad, any physical benefit deriving from a sport was banned. Some winners were recorded though, until the last Olympiad of 393AD. In 394, Roman Emperor Theodosius I outlawed the games at Olympia as pagan. Though it would have been possible to continue the reckoning by just counting four-year periods, by the middle of the 5th century AD reckoning by Olympiads had become disused. The modern Olympiad is a period of four years, beginning
Return period interest and formula_5 is the counting rate. If the return period of occurrence is 1 in 234 years (formula_5 = 0.0043) then the probability of no occurrence in ten years is In a given period of "n" years, the probability of a given number "r" of events of a return period formula_5 is given by the binomial distribution as follows. In the limit of :formula_11, such that formula_12 then Take where Given that the return period of an event is 100 years, So the probability that such an event occurs "exactly once" in 10 successive years is: Return period is