Littlewood's law states that a person can expect to experience an event with odds of one in a million (defined by the law as a "miracle") at the rate of about one per month.
The law was framed by Cambridge University Professor John Edensor Littlewood, and published in a 1986 collection of his work, A Mathematician's Miscellany. It seeks among other things to debunk one element of supposed supernatural phenomenology and is related to the more general law of truly large numbers, which states that with a sample size large enough, any outrageous (in terms of probability model of single sample) thing is likely to happen.
Littlewood defines a miracle as an exceptional event of special significance occurring at a frequency of one in a million. He assumes that during the hours in which a human is awake and alert, a human will see or hear one "event" per second, which may be either exceptional or unexceptional. Additionally, Littlewood supposes that a human is alert for about eight hours per day.
As a result, a human will in 35 days have experienced under these suppositions about one million events. Accepting this definition of a miracle, one can expect to observe one miraculous event for every 35 days' time, on average – and therefore, according to this reasoning, seemingly miraculous events are actually commonplace.