I've been wondering when Dumbledore concluded that Harry was carrying a piece of Voldemort's soul inside him. Did he know immediately, when James and Lily were killed? Or did he have to work it out over the years as he did with the Horcruxes? In Deathly Hallows, Dumbledore tells Snape:
‘Tell [Harry] that on the night Lord Voldemort tried to kill him, when Lily cast her own life between them as a shield, the Killing Curse rebounded upon Lord Voldemort, and a fragment of Voldemort’s soul was blasted apart from the whole, and latched itself on to the only living soul left in that collapsing building. Part of Lord Voldemort lives inside Harry, and it is that which gives him the power of speech with snakes, and a connection with Lord Voldemort’s mind that he has never understood. And while that fragment of soul, unmissed by Voldemort, remains attached to, and protected by Harry, Lord Voldemort cannot die.’
Deathly Hallows - pages 551-552 - Bloomsbury - chapter, The Prince's Tale
When did Dumbledore realize a piece of Voldemort's soul had latched itself onto Harry's soul?