ive always considered a classic car to be anything old enough to be rare. if its out of the ordinary, its not just normal traffic anymore. i also believe that there are also different eras of classics. retro is 80s-90s, vintage is 60s-70s, classic is 40s-50s, and anything before that is antique. however thats just my opinion, and its an opinion from someone who just got out of high school, so not worth very much.