Do the math Re: Medieval attitudes was Saving Harry

[houyhnhnm102]

No: HPFGUIDX 137819

nrenka:
 
> Good!Snape would also have been keeping up something of a front 
> towards those of Voldemort's supporters who were free, no?  That's 
> always been one postulated reason for his showy nasty behavior to a 
> young Harry Potter, being as Voldemort was not back and active when 
> Harry arrived at school.  If we have a Self-Interested!Snape,
>playing both sides as best he can, he's not under the same kind of
>strain as your committed Evil!Snape.

houyhnhnm:

Right!  So why don't we ever see Snape shmoosing the good guys (if
he's trying to fool them), when he can be smooth as silk with the DEs.  


nrenka:

> I can't quite find all the canon to match, but I'm under the 
> impression that everyone else is having trouble making the timeline 
> for Snape's teaching at Hogwarts, defection, and everything else 
> match up exactly.  This could be 'ooh, maths', it could be a case 
> where it works if you tweak it one way (but without cold hard 
> evidence), or it could be deliberate.

houyhnhnm:

I think the math[s] is pretty straightforward.  Wihtin a very short
space of time, Trelawney tells Umbridge that she has been at Hogwarts
for 16 years and Snape says he's been there 14 years.  This means
Snape has to have been hired by Dumbledore at least two years after
the prophecy was made.

So Snape is coming to apply for a job at Hogwarts as a real Death
Eater, under Voldemort's orders so he can spy for LV.  He happens to
arrive just when Trelawney is there for the divination position,
listens at the keyhole, overhears part of the prophecy and reports
back to Voldemort.

Two years pass.  Something turns Snape against Voldemort--probably it
is more than one thing  (I suspect Snape becomes disillusioned with LV
himself), but could include LVs plan to assassinate the Potters and
Snape's life-debt to James Potter.  He goes back to Dumbldore, offers
to turn spy, and Dumbledore gives him a job at Hogwarts as the potions
master.