Five minutes into the past.

An hour into the future sounds useful, but I think I'd spend the entire hour trying to avoid whatever I'd seen. Five minutes is just enough time to stop yourself from saying something stupid, missing a train, or forgetting your keys. It feels far more practical.

I'd go with five minutes into the past. Looking an hour ahead feels a little too tempting... I know I'd end up trying to live in the future instead of the present, searching for answers before I've even asked the right questions. Five minutes, though, are just enough to stop myself from sending an impulsive text, spilling my coffee, saying something unfortunate...

Besides, I like the idea of the future remaining a surprise. It loses a bit of its charm once you've already seen the spoiler. :)

I'd choose to go back five minutes into the past. An hour into the future might answer a lot of questions, but five minutes into the past could prevent some of them from ever existing.