The Librarian knew all about this sort of thing, it was part of what you had to know before you were allowed into L-space. He'd seen pictures in ancient books. Time could bifurcate, like a pair of trousers. You could end up in the wrong leg, living a life that was actually happening in the other leg, talking to people who weren't in your leg, walking into walls that weren't there any more. Life could be horrible in the wrong trouser of Time.

— Guards! Guards! by Terry Pratchett, Ben Aaronovitch, Peter Serafinowicz, and 2 others (Discworld, #8)