> go back in time
> "no one is there"
> change plans
> change SPAS12 to a barrel of petrol
> go to the moment when Thomas Mathus has been born
> pour everything with it
> the whole Malthus family dies
> go back to the present
> it's now a utopia without neoliberal capitalism and/or the world-wide rise of fascism
Yeah, they fly through some "portal" or whatever and end up in the previous day. Then langoliers show up to devour it. There's some other madness going on, too. You know, typical Stephen King shit.
Well, if we follow that logic, then where you end up is the emptiness of space, even if you go back exactly one year.
People tend to forget that the Earth not only goes around the sun, but the whole system is moving, so Earth is not in the same place as it was a year ago, even if it is relative to the sun.
Presumably all time travel devices, spells, etc. compensate for that. If someone figured out how to travel to the past, calculating where the planet was at the time should be easy by comparison.
It is a plot point in the sci-fi series Perry Rhodan, where they push the whole solar system 15 minutes into the future (iirc) to hide it from the rest of the universe.
For the "present" of the rest of the universe it is just empty space, the Solar System is in a bubble of spacetime completely disconnected from the rest and continuously shifted 15 minutes.