<P> The Balinese Pawukon is a 210 - day calendar consisting of 10 different simultaneously running weeks of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 days, of which the weeks of 4, 8 and 9 days are interrupted to fit into the 210 - day cycle . </P> <P> A 10 - day week, called décade, was used in France for nine and a half years from October 1793 to April 1802; furthermore, the Paris Commune adopted the Revolutionary Calendar for 18 days in 1871 . </P> <P> The Bahá'í calendar features a 19 - day period which some classify as a month and others classify as a week . </P> <P> The International Fixed Calendar (also known as the "Eastman plan") fixed every date always on the same weekday . This plan kept a 7 - day week while defining a year of 13 months with 28 days each . It was the official calendar of the Eastman Kodak Company for decades . </P>

Who decided there are 7 days in a week