I've been reading a lot of Roman history lately, and you run across things like, "The consul Tiberius Gracchus was murdered in 133 BCE. A decade later his brother, Gaius Gracchus, was himself murdered while serving as consul, in 123 BCE."
Man, I would think it would have driven them crazy, wondering, "Why are we counting the years backwards? And, hey, just what are counting backwards to? Just what's so special about 123 years from now, anyway?"
(Oh, and I always love the name of the period from the mid130s to the late 120s: the time of "the Gracchi brothers." It sounds like a shady Brooklyn trash-hauling company was in charge of Rome during those years.)