This is a parody of the old saying "it's 5 o'clock somewhere"... except that phrase used to refer to 5 PM. Which is to say, people are getting off work, going to the bar for happy hour, having a beer, etc. But in this case, it is much the opposite! This is much less fun and sometimes soul crushing! Because it is 5 AM in the dang morning, and you have to get up to feed a crying baby. That's why we laugh. We have to laugh so we don't also start crying.