I think overall the movie was okay, but could have been a lot better with even the most minor of twerks. At this point since I've seen about 85,000 time travel movies I'm not looking for an explanation on how it works, but the movie doesn't do a good job at following it's own rules which is indicative of making it up as they go along. Any good story needs an outline that needs to be followed or it can fall apart at the seems.

I don't understand why the movie basically presented it as a "one or the other" deal with Calvin and Sebastian. Like no matter what, [spoiler] one of them has to die.[/spoiler] That part being the main focus plot of the movie is never explained and really doesn't make any sense, so it being the "glue" of the movie it's easy to see how and why things start crumbling a bit here. Then there's the ending, like alright I can buy an open ending if the rest of the story is pretty much resolved but this felt more like they were like "Shit, there's no way we're gonna be able to explain this, let's just call it a wrap."

So yeah, it had potential and wasn't unenjoyable to watch, but the more you actually think about it the more you're like "Wait a minute though..."