What decade should the series have been set in?
The books are set in the 90s. Only Harry and Hermoine were raised as Muggles, most students weren't part of that other world. So it could be set in any decade.
Middle ages: Witch burnings.
50s: Brits were introduced to Wicca (neo-pagans).
60s: Hippies and new agers!
70s: Wicker Man and Zardoz!
Inspired by this 50s AI reimagining: https://www.youtube.com/watch?v=F8DqYX5Wui8