Depends on the rules.
Round trip to a 'read only' version of the past? I'd like to see the dinosaurs.
Round trip that can make changes? Probably a few hundred or even thousand years ago, so I could give them modern technology, information about climate change, try to educate people on social issues, etc. I'd create detailed instructions and try to make a religion out of it. There's no guarantee it would work, but I'd hopefully return to a solarpunk utopia. Honestly not sure if I would try this, as it would basically overwrite everything I've ever known.
One way trip? I'd probably pass, unless I can de-age. I would definitely want to go back to being a child with all my current knowledge.