Longest religious ceremony

Every 60 years or so - on a schedule determined by the position of the star Sirius in the night sky - the Dogon peoples of Mali, Africa, celebrate the Sigui, a mask festival which acknowledges the handing over of the cult's secrets from one generation to the next. The ceremony takes many years to complete - the last Sigui ran from 1967 to 1973, with the next due to begin in 2032 - as rthe men-only initiates must learn a secret language ("Sigi So") and carve a Great Mask, several metres in length. Each initiate wears their own mask and performs in a time consuming procession of dances from village to village. Sirius is the brightest star in the night sky, with an apparent magnitude of 1.47. Also known as the "Dog Star", it is a binary system, with a feint white dwarf companion star known as Sirius B.