Dumbledore tells us that DADA professor job at Hogwarts was cursed - no teacher lasted for more than a year - ever since Voldemort was denied the position.
"Oh, he definitely wanted the Defence Against the Dark Arts job. The Aftermath of our little meeting proved that. You see, we have not been able to keep a Defence Against the Dark Arts professor for more than a year since I refused the post to Lord Voldemort." - HBP.
Is it known from canon what year that event happened? In other words, how many years was the job cursed for?
(we know the curse ended in Year 7, after Voldemort's death, with Carrow being the last 1-year-termer).