Beat The Clock

(I work as a clockmaker. I phone a customer while standing at their front door after no response to the door bell:)

Me: “Hello, this is [My Name]. I’m here for your service call.”

Customer: “Well, I’m not home. I waited until 4:15 and you never showed up, so I left.”

Me: “You waited until 4:15 today?”

Customer: “Yes. You were supposed to be here at 3 and I waited until 4:15.”

Me: “I’m sorry, ma’am, but your appointment was set for between 3 and 5, not at 3. Also, it’s only just now 3:20.”

Customer: “What do you mean 3:20?”

Me: “The time. It is currently only 3:20 pm.”

Customer: “When I looked at the clock it said 4:15!”

Me: “By chance, would that be the clock I was coming to fix?”

Customer: “… Yes.”