How many days did the riot on which Detroit was based lasted? 
Detroit (film):  Based on the Algiers Motel incident during Detroit's 1967 12th Street Riot, the film's release commemorated the 50th anniversary of the event. 1967 Detroit riot:  Police confrontations with patrons and observers on the street evolved into one of the deadliest and most destructive riots in the history of the United States, lasting five days and surpassing the violence and property destruction of Detroit's 1943 race riot just 24 years earlier.
five days