Flint?

[constancevigilance]

I'm trying to put together a timeline of when horcruxes were made 
and with which murders they might be associated. I think I've 
encountered a problem in the Riddle murder timeline.

When Tom is asking Slughorn about horcruxes, he is wearing the ring 
which means he has already killed the Riddles. At this point, he 
doesn't know how to create a horcrux which means he hasn't created 
the diary yet. How much time can pass with a murder hanging out 
there before it can become a horcrux? We don't know, so we don't 
know if the Riddle murders are available to be used for the ring 
horcrux. But this is a discussion for another day. Back to the 
timeline problem.

Tom creates the diary using his 16-year-old self. Presumably he was 
actually 16 when he created it and it is likely that he used the 
murder of Myrtle for that horcrux.

The Lexicon places the death of the Riddles after Tom leaves 
Hogwarts, but this doesn't seem possible if he is already wearing 
the ring when he talks to Slughorn and before he has made any 
horcruxes. He must have killed the Riddles before Myrtle and before 
he left Hogwarts.

A flint or an error in the Lexicon?

CV