[throwaway9d0291]

I watch a lot of both American-made movies and TV shows as well as a lot of Japanese anime.

One thing I find curious is how different the models for time travel usually are.

In American media, it seems more often than not, time travel is modelled as if the past and the future are simultaneously existing parallel worlds, where the future is affected by the past in "real-time", e.g. Back to the Future's Marty gradually fading as the chances of his birth diminish, or Timeless's people in the future "watching" people arrive in the past and making sure their own team leaves "in time" to catch them.

These models don't really offer a solution to the grandfather paradox.

In anime however, time travel is near universally modelled with timelines, where time travel essentially creates a new parallel world each time. If you travel back in time and kill your grandfather, you simply create a timeline in which you were not born, but can continue to exist, because you are from a timeline where you were born.

I'm by no means suggesting that either model is unique to America/Japan (Rick and Morty for example uses the branching timeline model), I just find it interesting how they differ.

[caractacus]

I think it depends on the show in anime. SPOILERS FOLLOW. Erased is not a parallel world, but someone trying to change their past. Madoka finds Homura repeatedly doing whatever is possible to save Madoka. Steins:Gate is timelines and parallel worlds (think of how many times Okabe again and again tries to save Mayuri). Girl who Leapt Through Time is the Groundhog Day story, same day over and again; bit like Tatami Galaxy. No idea where something like Haruhi Suzumiya might fall where time is played with in many different ways.

Meanwhile Evangelion (the later films) and Attack on Titan both seem to be veering towards some kind of inability to stop the same grand narrative cycle repeating again and again...

[Izkata]

It also depends on the show in American media. Star Trek, for example, has nearly every version of time travel at some point or another - except the "simultaneous worlds" version described in GP with Back to the Future and Timeless.