Originally Posted by
savepoints
This is called a causal loop, and is, among other things, a "solution" to the grandfather paradox.
You know in the movie Timeline (2003) where they find the broken stone carving and Frances O'Connor's character is like "what kind of bitch would do something like this?" and then they go back in time and all the stuff happens and they need to escape through the wall but she sees that it's the same wall carving, except in the past, not yet broken, so she realizes and says out loud "Oh my god, I'm that bitch", and then she smashes the stone carving to escape. It's that thing, but like, science.
Or for a more recent example, and perhaps one from a more well-made movie, it's the thing in the Prisoner of Azkaban where all the weird stuff they see going on around Hagrid's hut and later the person who drives away the dementors is actually just Harry and co travelling back in time and avoiding themselves, but still doing the exact things they saw.
Point being, it's basically one of two most common "legit" solutions to the grandfather paradox, but unfortunately it's one of the worst tropes to exist, just absolutely awful.