Now I'm trying to figure out why I think it's set earlier, beyond just feeling that its world is obviously mid-Victorian rather than Edwardian. No doubt young English girls were looked after by ayahs in 1911 India, and there's no reason why an Edwardian Mary Lennox should have been taken from the station to to the Manor by anything other than horsedrawn transport. But then there are all the Bronte references, and the total absence of any reference to Dickon's schooling (surely after 1870 he should have been attending a board school, not larking about on the moor all day?). At one point Martha alludes to an anti-slavery motto ("Am I not a man and a brother?") that might have been less current in 1911 than in 1860. But these seem thin pickings, and short of actually picking the book up and having a look for more clues they're all I can come up with.
So, flist, when do you think TSG is set? Can the matter be settled definitively?