“Mostly non-obnoxious time travel story. As time travel stories go, this is about as good as it gets. By which I mean, it didn’t infuriate me.
Let’s do a quick rundown of time travel stories that work and why:
Back to the Future: Works because it’s fun. It’s Teen Wolf but with a time machine instead of a cryptid. The science is completely unimportant. It’s mostly jokes. And incest.
Demolition Man: Because Demolition Man works on every level. Fight me if you disagree. Physically fight me. It’s a perfect film. There’s a bunch of action set pieces, toilet humor, and a topless woman for absolutely no reason. I maintain that this may be the most gratuitous topless woman in film with the possible exception of the Friday the 13th movie where a girl takes her top off, swims IN THE DARK, and then gets out and puts her clothes back on and continues being in the movie, so there was no plot reason for her to go topless swimming.
Primer: This is the all-brains version of time travel, and it works because it doesn’t particularly matter if the viewer totally 100% follows the science or explanation. Also, because the idea of what they’re doing is to keep things contained and small, the plot doesn’t get into “Maybe we should kill Hitler” territory. If you want to go back in time and kill Hitler, that’s the core of your movie, not an incidental.
Bill and Ted’s Excellent Adventure: Because the idea of getting a time machine in order to pass a high school history class is so asinine, when you start there, you can do anything. Time travel exists so we can see Napoleon being a dick at a water park. Plus, Bill and Ted are dopey and likable, so you kind of can’t get mad at them when they do a stupid time travel thing and it actually works. Also, why is this a thing in movies and TV: Students are supposed to do a history project for school, and they find some weird, backwards way to do it, and the project IS better than the stupid poster boards or whatever that the other students bring in, but in my experience, teachers are dickheads who would be like, “Well, thanks for bringing ACTUAL Socrates to class, but you didn’t fill out the worksheet, and I don’t see your cited sources, so I’m afraid you get an F.”
Army of Darkness: I’m not totally sure why this movie has time travel. Maybe because at that time, it’d be easier to have a big medievil battle than a modern one with guns and shit? I dunno, but whatever the reason, it works. I think because the time travel motivates the character, but the story could easily take place in just about any time period. There’s absolutely NO talk about Ash affecting the future, messing with the timeline, whatever. It’s all just kind of vague, “evil happened because you’re a fuck-up” stuff.
Terminators 1 &2: Time travel doesn’t REALLY work in these, but they’re so cool that it doesn’t matter. After 2, things got a little too fucked-up for my liking. The series constantly begs the question: Why not just kill so-and-so’s great grandpa in the old west when they won’t even have anything that could take down a Terminator? “