If I could somehow time travel as an incorporeal presence, I would go far enough back in time to witness the beginning of the universe (assuming it had a beginning), then fast-forward to when the Earth was newly formed. I would then make stops every 200 million years so I could see how the planet's features and lifeforms changed over time and how close it is to the currently proposed geological history of Earth. (Microscopic vision would come in handy for this, but that's probably not part of the deal.) I'm also curious about how humanity will go extinct, what the planet will be like in the distant future after our extinction, and what it will look like when the sun becomes a red giant and vaporizes Earth, but seeing Earth at a very young age interests me even more because watching it develop and seeing its lifeforms go from simple to complex would be more interesting to me than watching its inevitable end.
If I’m confined to my fragile mortal body in this scenario, I wouldn't be able to go any farther back than the Cambrian period, so I would instead opt to travel to the year 2216 to check in on humanity and see all the knowledge we've gained since now, as well as which problems have remained, gotten worse, or been solved. That way I could better know how to do my part to prevent life on Earth from being worse for future generations, as well as educate others on how to do so. (Hopefully I won't be poisoned by nuclear radiation or something immediately upon arrival to the future.)