Does the Hyperborean Cycle of which Door to Saturn is set in take place in the Hyborian Age of CAS's friend Rober E Howard? If so, does that mean chronologically the Poseidonis stories are before? I have been confused at times of which age was before the other.

The worlds of Smith's Hyperborea and Howard's Hyboria are distinct. As to age, Smith's Hyperborea is set at the very beginning of human civilization, just as Zothique is set at the very end, and the characters in Smith's Poseidonis tale "The Double Shadow" already consider Hyperborea to be prehistoric, with only a few tantalizing records and artifacts.

Jim