Given that Avengers: Endgame has a runtime of three hours and one minute, it’s easy to imagine the story would use that time to build up to an epic showdown with Thanos, but some new clues point to a much earlier rematch with ol’ Grimace… and a big loss for our heroes.
Establishing a Timeline
It’s tough to tell when anything takes place in any of the Endgame trailers, but one big clue comes from Black Widow’s hair. We see three distinct styles: her short, blonde Infinity War cut; a mid-length ponytail; and a long-haired red look with blonde tips. For her hair to grow that much, several months need to have passed (at least), which implies Endgame has a couple time jumps.
Source: IGN.com Signs Point to an Early Loss for the Avengers in Endgame