Timeline Questions re Snape's and Trewlaney's Appointments

[potioncat]

No: HPFGUIDX 150919

Angie asks:
> In OOP, Harry turns 15; Trewlawney said she'd been teaching for 16 
> years; and Snape said he'd been teaching for 14 years.
> 
> So, Trewlawney started teaching the year before Harry was born?  
And 
> Snape the year after?

Potioncat:
That is my understanding, although I don't think it's certain how 
long before Harry's birth Trelawney started teaching. It crosses my 
mind that the math doesn't work out...but it never does.  
 
>Angie: 
> So, we have a two-year gap b/w ST's appointment and Snape's? I 
can't believe DD caught Snape eavesdropping two years 
> before and just let him go -- I guess I don't understand what Snape 
> was doing during the time b/w the eavesdropping and his own 
> appointment.

Potioncat:
Well, what if Snape was at the Hogshead to defect...on his own? 
Depending on whether you believe the Black Family Tree or prefer to 
reason it out from the text, Regulus may already have died. Snape may 
have been looking for a way out too. 

DD tells Harry that the eavesdropper was in LV's employ, so he 
probably already knew that at the time. So, Snape is there to defect, 
overhears part of the prophecy and works out a plan/is given a plan 
to tell LV part of the prophecy.

I find it hard to understand how DD would just let Snape go if he 
knew Snape was a DE; but I find it harder to believe DD didn't know. 
It hurts my mind less to think that Snape was in LV's employ but had 
turned to DD at that point.

I'm not sure if Snape was already there to apply for a teaching job. 
That's what Trelawney thinks, and she may be right. So he applies and 
is turned down. That's not too surprising. He's still pretty young. 
No big deal the job will open up the next year. It may always have 
been Snape's desire to teach DADA. LV may have been using that. Who 
knows whether it was LV's idea to put Snape in Hogwarts or if Snape 
suggested he could serve at Hogwarts? Snape gives LV the credit for 
it, like a good little minion.

 Angie:
> I also wonder if Snape would have been appointed to HW had DD not 
> caught him eavesdropping and had LV not taken a turn for the worse 
in 
> GH.  (I assume even DEs need paying jobs.)

Potioncat:
Snape turned before LV's fall. So he had been working for DD a few 
weeks to years. The fact that he turned spy at great risk, makes me 
think it was months to year(s). We don't know, but it seems to have 
been some time. 

I assume all the DEs had day jobs. Snape could have been making 
potions at an apothecary, or at St. Mungo's or he could have been a 
Spellbinder, making spells stick to magical objects.(I made that up.)
 

Angie:
> Also, why was Snape eavesdropping in the first place?  Probably on 
> LV 's orders, but why?  ST didn't have a rep for being a successful 
> seer, after all.

Potioncat:
I think it was just luck. I think Snape was there to either apply for 
DADA or to defect or both and he was there at the right time. I would 
think he knows how to make Felix Felicis (even if I can't spell it.)
>
 
> Angie (who's never been good with "the math" and hoping this makes 
> sense)

Potioncat who isn't good at this math either, but thinks we're in 
good company with a certain author.

This line of reasoning would work out for a nonDDM!Snape, if you 
assume he was there on LV's orders to get the teaching job and begin 
spying for LV.