I think the general opinion is that once it's built; that is the point where you can go back to. Like once you turn it on someone would walk out at that time, initially to just prove the theory to the creator. The fear is that people may just start pouring in immediately as well because of a distant future crisis or something too.
Actually, Stephen Hawking spoke about the idea of time travel is impossible, going back in time. We only have the potential to move forward. (I don't know the entire theory so please if you have questions google is your friend.)
A friend of mine was making some theory about it (can't remember how it went, it was a while ago), it said something regarding the speed of how fast we would travel, and the effects it would have in our bodies. But I'm after a while he started making some stuff up since he started sprouting some other nonsense that had nothing to do with time travel because he was kinda drunk at the time; so I'd take that really lightly, cuz I don't know when the alcohol started making some effect on him
Actually time travel is impossible the only way to do it is to rip a literal hole in space time and we know that that's an irrelevant idea, or at least one that isn't feasible.
Of course there is disagreement about whether or not retrograde time travel is possible. Technically, physics does not forbid it, but we obviously have incomplete physics. We don't even know if there is only one time dimension, and we cannot be certain as to our spacetime topology. As far as I know, the assumption is still k=0 based on dark matter and dark energy mass contributions, but we don't really know what those are, either. So, until we can figure some of this stuff out, we won't be hopping onto extra time dimensions and circling back into the past. My advice: vote on people to support science funding (and not just applied science).
Unlike some *cough* OTHER people I know.