I do believe that while Obi Wan simply aludes to the time period when he knew Luke's father, Anakin Skywalker, as "before the dark times; before the Empire", Luke picks up on the allusion and attempts to confirm by asking, "You fought in the Clone Wars?"
If I'm not mistaken this reference to The Clone Wars has been intact ever since the 70's theatrical release.
I recall as a 9 yr old and for many years after that wondering, "what in the world could the 'clone war' be?" Until AOTC's release that is...