death to capslock

I know that a lot of fandom agrees that Tom left Britain sometime in the late 40s and returned in the late 50s, but I'm wondering how much evidence we really have for this timeframe. I don't think we're told how long Tom worked at Borgin and Burkes before he left. Fudge says in HBP that the Ministry has been trying to catch Tom for almost three decades, so we know that the latest that Tom might returned to Britain is about 1966/67. And we know that he returned sometime after Albus became Headmaster. However, we don't seem to have a very firm date for when Albus was appointed, nor do we know how long Albus had been headmaster before Tom showed up for an interview.