The Vintage Bicycle Association puts the cutoff in the mid-1980s. Road bikes before that date consistently had toeclips, 5- or 6-speed friction shift, lugged steel frames, and either centerpull or single-pivot sidepull brakes. Since mountain bikes evolved a bit later, I would put the old-school / vintage demarcation closer to 1990, before front suspension appeared.

I think everything I own or ride (see signature) qualifies as vintage, including the rider.