I'd love to be a teenager in the 50s (because of the film Grease) but I love the 80s for its music (not all of it; some of it was awful, but most of it wasn't).
About 1923 or so during the Roaring Twenties! What a great time to live and feel alive!
You can't travel forward because it doesn't exist yet. If you go back you shred the fabric of space and time in a paradox scenerio that makes everything not have existed. And don't say "But if you could ..." because even if you did travel in time it would create a whole new reality and you wouldn't be where you wanted to go anyway.
1985 to see myself being born. That would be amazing.