I'd choose the decade from 1967 to 1977. Start off at the beginning of free love and counterculture, when there was no AIDS, promiscuity was encouraged, responsibility was despised, drugs were good for you, music kicked ass, and all sorts of craziness was going on. For those of you who like war and killing people, there was Vietnam. Not as cool as WWII, but when you got home, rather than marry your high school sweetheart, have kids, and live a normal, boring life, you could sleep around, get bombed out of your mind on the era's great acid, and there was still disco and key parties to look forward to in the next decade. Your trip would end in 1977, where you could catch the premier of Star Wars, and get home before 1978 comes around, when the first AIDS case was reported, and people began discovering drugs may be harmful.