Well, completely ignoring the PT, I get the following.
Luke. In ANH we find that Vader hunted down the Jedi. Luke’s father died (in ANH there is nothing linking Anakin and Vader). So we can come to the conclusion that the events where the Empire rose were not earlier than Luke’s conception. Anakin knew of Luke’s at least impending birth before he died.
Leia. Kenobi severed her father in the Clone Wars. This doesn’t tie specifically to Leia’s age, but does pin down her father being of the generation of the Clone Wars.
Kenobi. He speaks of the Jedi, before the Empire, before the Dark times. There is no clear link between what he says and the Clone Wars, only that he and Anakin both fought in the Clone Wars. So Kenobi, Anakin, and Leia’s father were all in the clone wars in some capacity.
All of that agrees with the PT.
In TESB we get a more firm timetable of the Empire with Vader being Luke’s father. We do hear Luke thinking Dagobah is very familiar, but we don’t get any reason why. From the context of the film it was most likely a force vision.
In ROTJ we find out that Luke and Leia are twins. This firmly plants the start of the Empire at their birth. Why? Vader did not know Luke had a sister which means he was not present at the birth. So the event that turned Vader and started the Empire happened between conception and birth of the twins.
We still have no indication of when the Clone Wars took place. It could be a month before or a decade before.
From the actors it is also hard to guess. Alec Guiness was was 63 when ANH was released. Sebastian Shaw (true he wasn’t cast yet) was almost 72. Phil Brown was 61 and Shelagh Fraser was 56. So Alec, Phil, and Shelagh were contemporaries and from the dialog in ANH, Sebastian was cast to show how the Dark Side had aged and warped him. Anakin was Kenobi’s student. When you look at the ages in Attack of the Clones, the relative ages of Kenobi, Owen and Beru are not that different, 31, 27, and 18) from the ANH cast (63, 61, 56 about 30 years older). So Anakin was young enough for Kenobi to train (also remember that Yoda said Luke was too old in TESB, so Anakin would be younger than Luke… by a lot). So Sebastian’s advanced age much have had a reason beyond Anakin actually being older than Kenobi.
So from the casting and the dialog just in the OT, the Clone Wars had to have taken place somewhere between 30 and 20 years before ANH. Officially it was 22-19 years before. So all the timings of the PT fit with what we see in the OT, except the age of the actors. But there is also nothing in the movies indicating how long the Clone Wars lasted so adding in another 5 to 10 years of war doesn’t break anything. Also, Ahsoka appears to have grown up considerably more than 3 years, and she is introduced when the Clone Wars are well underway (Anakin was still a Padawn when they started). So the official timeline seems too short and doesn’t really fit with the ages of the actors cast in both the OT and PT.
As a side note, Jimmy Smits was much older than the others in AOTC, but he was contemporary by the time he appeared in Rogue One (he was 61 when it was released).
^ based on the above ,an idea popped in my head …it seems logical to me that Anakin should have been 15 years old at the start of the prequel trilogy . That would have made him fairly substantially younger than Luke at the start of his journey in the OT , without straying into the kiddie territory with Anakin being 9 years old in episode 1 as released . I wonder if Lucas had the thought that making Anakin 15 at the start of the PT would be straying too close to Dune ,what with Paul Atreides being 15 in the first book and being part of a chosen one prophecy in the sense of Paul being a prophecized messiah . Maybe he realized how much he borrowed from Dune in the OT already ( among many other sources ) , looked over at his son who was a toddler at the time , and decided on placing Anakin at 9 years old as a happy medium between 9 and 15 so that it wouldn’t be too on the nose derivative of Dune . Probably a stretch ,but I find it fun to think about . I would still like to have had Anakin start out at 15 in episode one anyway . I vote 30 to 25 years before ANH as the start date of the Empire .