The only
model which
makes sense (
apart from the fact that time travel doesn't make sense) is having a single time. Travel back in time and change something? Well, it was already changed (by
You Know Who) before you left! Attempt to change some
outcome? Before you bought that overpriced
ticket for the
2020 model
ChronoGo H2, you'd already did (done?) what you'd do (did?), and you already know the results.
Or, in other words, Nothing Happens.