11 Scenes From the New Avengers: Endgame Trailer That Are More Important Than You Think

A very important note here is that Natasha's hair goes from an ice-blond bob to her signature red waves. In this scene, it's obvious that her hair has grown out of the color, since we see her ends are still pretty light (guessing her usual stylist was dusted along with everyone else). Since we doubt Black Widow decided to switch wigs to do battle, it seems enough time has passed for her hair to grow. Considering how long that would actually take, we'd have to say that at least six months pass between the beginning of the film (where she's blond) and this moment.