Have not gone back through the whole thread, so I apologize if the following was already mentioned.

Red Leader (played by Drewe Henley; who was 36 at the time of filming) said he met Anakin Skywalker, the renowned fighter pilot, when he was “just a boy”. If we assume Red Leader was supposed to be the same age or a little older as the actor who played him, what tentative conclusions can we draw?

So I would say that The Empire was formed between 25 to 35 years before The Battle of Yavin. But the PT version is still possible if we accept Red Leader as younger then he looks. It depends on what age range we see someone being a boy rather then a man