Classic is appearance/ethos.
Vintage is age.
There is no hard cutoff for what applies, but some general views are-
- must have lugs
and/or
- a level top tube
and/or
- friction shifting
and/or
- downtube shifting
Here a modern steel bike that I guess would be classic as the frame is classic in appearance with a level top tube and lugs. But it was made a couple years ago and is definitely not vintage in age.
But ultimately there are no absolutes. Old balloon cruisers weren't lugged, but are c&v. Indexed late 80s road bikes are c&v.
Etc etc.