Olympiad Olympiads for the summer and winter games, and such usage particularly for the Winter Olympics is not consistent with the numbering discussed above. The U.S. Olympic Committee often uses the term "quadrennium", which it claims refers to the same four-year period. However, it indicates these quadrennia in calendar years, starting with the first year after the Summer Olympics and ending with the year the next Olympics are held. This would suggest a more precise period of four years, but the 2001–2004 Quadrennium would then not be exactly the same period as the XXVIIth Olympiad. A "Cultural Olympiad" is a concept
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