"Turn of the century" usually refers to 1900-ish, at least in popular use.
Other stuff we know:
-Wasikowska plays a young author who discovers that her charming new husband isn't who he appears to be. Given Hunnam's quotes, I'd wager Cumberbatch is the husband while Hunnam is probably a friend who has a crush on her.
-Cumberbatch and Chastain are playing brother/sister from an aristocratic family.
-First part of the film takes place in America, then moves to England. Also it starts out as a love story but then becomes dark.
-It's R-rated.