This is ridiculous and arbitrary, but let's define classic as anything written pre-1900.

I almost never read contemporary fiction, certainly not past 1960. To me, if an author is long dead -- and I know this is stupid, but it's one of these irrational, vague internal feelings -- they become more of a mythical figure than a real person, and by extension, their work seems to become real events that happened, blending into actual history in my imagination. Whereas if I read a modern book, and especially if the writer is still alive and lives in the same era I do, it's more apparent to me that I am just reading a made up story by a regular person who happened to write down one of his silly daydreams.

I think the most recent novel I've read as an adult is Pale Fire (1962). But most of the fiction I like is in the 1860s.