With Annabelle: Creation taking place firmly in the 1950s, the fact that The Nun could take place in the 1940s or early 1950s seems to corroborate that idea.
However, what’s surprising about the setting of The Nun is just how close it is to the other Conjuring movies.
Certain sources associated with the development of The Nun had previously suggested that the film would mark the chronological beginning of The Conjuring universe.
With a decade separating the events of The Nun and Annabelle: Creation, the timeline being established by these films appears to be pretty tight, meaning it could still somehow potentially tie into the lives of Ed and Lorraine Warren at some point.