Note, that time references are not exactly fixed.
Each new generation tends to pick it's own time references.
"Classic" is often used for something that is suddenly made obsolete by a technological leap, yet is still embraced by the generation it was introduced to.
I am sure that there were some adds for "Classic" steel frame bicycles when alloy and titanium frames first made giant in-roads into the cycling community.
If there was to be another leap in techology (lets call it plastitianyite) to mfg. 2 oz, STIFF, aero frames, that you could run over with D9 Cat, then all those carbon frames could suddenly become "Classic".
So, if Bianchi switched all their production to plastitianyite frames in 2013, all the 2012's could suddenly become "Classic".
None of the time frames in my earlier post are engraved in stone. The time frames were set for judging classes in a motorcycle environment, and there was a lot of heated discussion to get there.
As I recall, the time frames pretty much matched some of the more prestigous organized motoring events, in North America, The UK, and Europe.
If somebody called one of my bikes a "Classic", I (personally) would take that as badge of honor and not as a slight.
Classic def. http://en.wikipedia.org/wiki/Classic