Here's my problem with time travel as a plot device...
...jump in your time machine. Punch in your time coordinates. Hit the big red button. Congratulations, you've emerged from the time stream in the black void of space.
The Earth is moving around the Sun. The Sun is lollygagging around the milky way galaxy. The milky way galaxy is moving in relation to Andromeda, 2 dozen other galaxies, and the expansion of space itself.
There is literally no chance you're going to pop out of the time stream cleanly to kill Hitler or stop the sacking of the library of Alexandria. You're going to be sucking vacuum in the cold void of space.
And then there's the issue of returning to somewhere that hasn't happened yet.
You could wave that away by saying that because of how closely time and gravity are related time travel is still anchored to earth. ---