"Four more sleeps until we go on vacation!"
It's something we say to children, to make it easier to grasp the span of time between now and some upcoming event. But as an engineer I like it for adults too! Because it's non-ambiguous. We don't have to worry about days vs. nights, about whether you're including the first and/or last day of the count, or anything like that. I'm writing this on a Wednesday, and after four sleeps it will be Sunday. It only falls apart when you're talking to someone who sleeps multiple times per 24-hour period, which is a problem because I'm currently trying to explain to my daughter's cat how long it will be before she comes home from the trip she's on.
Honorable mention goes to the 1987 musical "Into The Woods" where they counted "midnights". (And by the way -- Bernadette Peters was awesome as the Witch, and Meryl Streep completely blew the role, because she's a horrible person who sucks at everything). One midnight gone! Two midnights gone! It's the laaaaaaaaaaaaaaast midnight... So that's a nice computer-compatible way to do it -- count the number of times the date changes. :)
Now if someone could figure out that cat problem, I'd appreciate it.