@irvmull
Reasonably, if you went back in time exactly 30 years, then the Earth would be exactly where it was 30 years ago.
No, besides the Earth spinning and travelling round the sun, also the sun is travelling round the galaxy as it turns, also has some proper motion therein (it bobs up and down), and also the galaxy is fair shifting. Even ignoring the last three (which each have more effect than the first two), if you choose a time which has the Earth in exactly the same place in its orbit, the time of day will be different, so you'd be in a different place on Earth - possibly inside solid rock or 5000m above the ground, or more likely 100 miles out to sea. The Earth's rotation rate isn't quite regular (leap seconds), the continents are zipping around in slow motion, and its orbit round the sun isn't quite regular - it becomes more and less circular, and the perihelion will be affected by relativity just like Mercury's (but somewhat less so). You need to posit something like a wormhole anchored at both ends, where something in-story ensures the ends are at the 'same' place, or at least compatible - but then, they wouldn't even have to be on the same planet.