Longest religious ceremony

Every 60 years or so, the Dogon peoples of Mali celebrate the Sigui, a mask festival which acknowledges the handing over of the cult's secrets from one generation to the next. The ceremony can last for more than five years – the last Sigui ran from 1967 to 1973, with the next due to begin in 2032. The male-only initiates must learn a secret language ("sigi-so") and carve their own great mask, several metres in length. Each initiate wears their own mask and performs in a procession of dances from village to village, which is why the ceremony can last for several years.

There are some claims that the 60-year period corresponds with astronomical observations, but these appear to be a misinterpretation; that period is chosen as it aligns with the Dogon's expectation of a "lifetime", with the idea that every man should witness a Sigui festival at least once in his life.