There is something else that is never addressed. Where we were in the past in terms of space is very different to where we are now since the earth /solar system/ galaxy and who knows what else are all in motion.
I remember a Science Fiction short story about a man who had invented a time machine, which of course needed lots of energy. He planned his first trip to begin at the local electric power-plant, which was closed for generator maintenance.
The departure point was from within the shell of a giant generator whose rotor was out for maintenance. The trip was supposed to last for two hours. When the man did not return by the next day or week or month, his engineer friend assumed that he had been killed in the past.
The work was completed on the generator rotor, it was reinstalled and brought back on-line. Some time later, in the middle of the night, the engineer friend sat up in bed having suddenly realized the error the time traveler had made in his return calculations. As he reached for the phone to call for the shutdown of the generator, he heard the explosion at the power plant several miles away.
The time traveler had returned to his point of departure inside the shell of the generator. His mass of 180 pounds had been added, off center, to the rapidly spinning rotor. The resultant imbalance tore apart the generator, shorting the circuits, etc...
“It has long been an axiom of mine that the little things are infinitely the most important.”
― Arthur Conan Doyle,
Exactly!
I've brought this up many times in time-travel discussions. The Earth, she rotates. She also travels around the sun. The solar system travels around the galaxy's rotation. The several galaxies in our local group have relative motion relative to each other. The universe itself appears to be expanding. Taken together the cumulative Delta-V is significant. If you want to go back to see the dinosaurs, you're going to need not only a time machine, but a spaceship with an FTL drive, and damn good records of the relative positions of not only our sun within it's galaxy, but the motions of the Local Group as well.
The computation required just to find your way home would be ... astronomical.
All that said, I still really like time travel stories, as long as the writer remembers causality. Breaking causality pisses me off.