Time

Try explaining the end of Daylight Savings Time to my cats, and how the clocks were turned back one hour, so that their dinner might seem like it's an hour late, but it's really "on time."

Actually, the cats have made it apparent to me how arbitrary and unreal "clock time" actually is.

Eat when you're hungry, sleep when you're tired, move your bowels when nature calls.  Chase the occasional chipmunk when the opportunity presents itself.  That's cat wisdom.