Unfaithfulness in the keeping of an appointment is an act of clear dishonesty. You may as well borrow a person’s money as his time.

Lateness is a transfer of cost rather than a personal quirk. The half hour someone spends waiting was taken from them without asking, and it is gone in exactly the way money would be, except that nobody itemises it. Habitual lateness also carries a message the latecomer never intends to send, which is that their time is the one that counts.

Treat appointments as fixed rather than approximate. Leave earlier than you need to, and if you are going to be late, say so the moment you know rather than when you arrive. It costs you nothing and returns the choice to the other person.