I guess in a way I can understand why people have such a variety of impressions on the temporal setting of Daughter of Mystery. As I noted elsewhere, the events are primarily domestic to Alpennia and the tightly-filtered point of view means that the characters have little reason to comment on the specific time-frame. But really, it's full of clues. (There's even a reference to a specific year when Barbara is trying to track down when her mother might have been a student at St. Orisul's.)