Why spare Lily?

[aggiepaddy]

No: HPFGUIDX 105043

Leah said  <HUGE snip>
 Why? Did he have to get to 
> Harry before midnight on 31 October, (possibly the anniversary of 
> Harry's conception) and if so, why?  Did he have to get to both 
Harry 
> and then Neville on the same day?
  

Aggie says 
Personally I think that this is a very intersting observation.  If it 
was the anniversary of H's conception would that have contributed to 
the protection spell? Is it just coincidence that it's Halloween?  I 
don't know if it would have any bearing on the outcome of the story 
but I just wanted to say, "Well observed!!"