You’d have to choose going back in time wouldn’t you? I’d go back to 1888 and see who Jack The Ripper was assuming you could actually hover above the East End in an invisible bubble or something then I could follow him and learn who he was. It has bugged me for yonks.
There is no point in going forward as there is probably nothing worth going forward for – man will have destroyed the planet within a generation or two – if not by global warming then by some idiot terrorists / "rogue" state obtaining and using a nuclear capability.
As for going back in time – I wouldn’t mind going back to meet some of the great scientists and thinkers – in particular Harvey, Newton, Galileo and, especially, da Vinci.
Then on the way back visit some of the greatest Courtesans in history
I would turn it into a TARDIS and try to mess up the mechanism so I only have a vague idea where it will take me. Wear my Third Doctor velvets ruffled shirt and silk lined cape and take a teenage girl with me!
Wherever I go I will remember the effects of the Blinovitch Limitation Effect.
I would like to head for the American civil war, 19th Century rural Appalachia, solve the mystery of the princes in the tower and then hop forward in time and see if I can avert the Dalek Invasion of Earth in 2150 or 2164 depending on what date you believe it happened or will happen.
But that Blinovitch Limitation Effect is problematical. See The Day of the Daleks if you do not believe me.