Maybe the 50's, before so much technology but still had still had many conveniences.

During the construction of the pyramids in Egypt to video the guys who made them and if they really deliberately aligned the pyramids to the Belt Of Orion and maybe chance upon Optimus Prime.

September 11, 2001 to video from different angles the crash of the two planes.

. . . but Dr.Emmett Brown hasn't replied to me yet. Maybe the DEA confiscated his DMC sports car and he's got a Tesla Electric now. Still no word from Capt.Kirk and Scotty. I don't know if the Vulcan has a comfortable ride as compared to Han Solo's rugged Millennium Falcon. Oh, well, I'll just keep waiting here with my thumb up to hitch on any passing craft that can make a jump to hyper space

Hard to choose one, but perhaps some of ancient Egypt. I'd want to observe and study some of the periods before and after King Tut, and the pyramids for educational purposes. As long as I'm not stuck in the past, and I can return when ready; cool