Norman's Awesome Experience

Contrary to what you might think, this *isn't* a knock-off of "Bill & Ted's Excellent Adventure". Sources differ on the exact release dates, but it was at the very least in production before B&T came out. The plot is quite different (except for the bare fact that time travel happens) and it's pretty clear it was retitled to cash in on the more successful movie's reputation.

It's not a particularly great movie, but it doesn't aim to be Shakespeare. Aside from the time travel itself, what happens is technically feasible, and the story points out the realistic difficulties even a knowledgeable modern person would have just surviving in, much less changing, the past.