Passage: In 2020, human boxers are replaced by robots. Charlie Kenton, a former boxer, owns "Ambush", but loses it in a fight against a bull belonging to promoter and carnival owner Ricky, who rigged the fight to mess with Charlie as he sees him as a joke, partially because he beat him up the last time they competed for bailing on the bet. Having made a bet that Ambush would win as a result, Charlie now has a debt to Ricky that he can't pay—which he runs out on.

Question: When are boxers replaced?
2020