Factual error: Toward the beginning of the movie, the boss of the family at the time, Carmine Galante, is shown getting out of a car as the crew watches in awe. Soon afterward it is learned that he was murdered and Leftie is seen in Donnie's car holding a newspaper with Galante's famous post-mortem photo, cigar in mouth, on the cover. Later in the chronology of the movie's events, when the crew is poolside in Florida, Sonny Black is holding a newspaper with a cover story that John Wayne has died and he asks, rhetorically, "How can John Wayne die?" The problem is that the movie's chronology is way off. John Wayne died on June 11 1979, a full month before Carmine Galante was murdered in a Brooklyn restaurant on July 12 of that year.
Factual error: In the beginning of the movie when Lefty asks Donnie if he is Don the Jeweler, Donnie turns to the man behind the bar. On the bar shelf there is a bottle of Absolut Vodka. The movie was set in 1978, and Absolut Vodka was first launched in 1979. The design of the actual bottle in the scene was launched even later. (00:06:20)
Factual error: In the scene where Depp visits Pacino at home during Christmas, Pacino is watching TV. On Pacino's TV stand are VHS tapes, including some movies that where not made until after 1978, when this film is set: Death Wish 2, After The Fall Of New York, House, Low Blow, Ghoulies and The Last Dragon.