It is possible to travel in time, while having an OBE. Because nothing's impossible when it comes to the astral.
You can watch your two-year-old mother, or your two-year-old daughter. There's no time/place, Just what you want.
I would agree with Nitya though, The past has happened before, no one can change it now. But future is just a possibility.
Well imagine you travel in time and see your friend getting hit by a car, so you go to warn him about it, and when he's crossing the street you scream "stop" and he suddenly stops, then gets hit by a car.
The same could happen another way, that you warn him and he runs as fast as he can, and saves himself. You can never know.
Even if you don't warn him, maybe he saves himself, maybe he doesn't. Look, there's always another possibility.
Things may happen a different way, for example maybe he decides to stay home.