(How young was he when he started following Dumbledore, anyhow?)
Assuming the hilltop meeting is during late fall or early winter after Harry's birth - almost 21.
Why would it be after his birth, when they both seem to refer to a child yet to be born?
Also, this would not line up with Severus's statement to Umbridge in OotP (fall 1995) that he had been teaching there for fourteen years, which counts back to 1981. Given the weather/landscape clues, that meeting was well into the winter, certainly not in the summer before the start of the 1981 school year, therefore it most likely took place at least the previous winter (late 1980-early 1981). And at that point he'd already been employed doing some spying regarding Dumbledore - it's possible the interview where he overheard the prophecy was the previous spring, ca. March 1980. If that's the case he was not long past twenty.
Assuming the hilltop meeting is during late fall or early winter after Harry's birth - almost 21.
Why would it be after his birth, when they both seem to refer to a child yet to be born?
Also, this would not line up with Severus's statement to Umbridge in OotP (fall 1995) that he had been teaching there for fourteen years, which counts back to 1981. Given the weather/landscape clues, that meeting was well into the winter, certainly not in the summer before the start of the 1981 school year, therefore it most likely took place at least the previous winter (late 1980-early 1981). And at that point he'd already been employed doing some spying regarding Dumbledore - it's possible the interview where he overheard the prophecy was the previous spring, ca. March 1980. If that's the case he was not long past twenty.