35 years

Neah killed all of the members of Noah clansmen except the first and ninth disciple and was killed by the Millenium Earl instead, but before he died Allen offered himself to be his host until the day Neah is ready to finish what he had started. Now, what if the Allen Walker we know had the recollection of what happened prior to thirty five years? I DO NOT OWN D. GRAY- MAN.