What’s the difference between fashionably late and straight-up rude? We asked three experts.

There are two kinds of people in this world: those who find it acceptable to be a little tardy and those who consider it an affront to all that is decent. As someone who frequently runs late, I’m often relieved when someone else is, too. And I don’t mind if a friend is a bit behind; the worst-case scenario is I have a few minutes of peace in which to stare at my phone. But the perpetually punctual see this as disrespect, as showing up late is a sign you don’t value others’ time, that you…