This is a story told by Earl Nightingale.

There was a jeweler who noticed that a certain man would stop in front of the jeweler’s shop every morning at the same time, look in the window for a minute, and then go on.  He never came in the shop, he just stopped and looked.  One day the jeweler’s curiosity drove him to go out and ask the man why he was stopping there every day.  The man explained that he was the one responsible for blowing the noon whistle at the factory down the street, so he was setting his watch by the clock in the jeweler’s window.

Interestingly enough, the jeweler was setting the clock in the window by the factory noon whistle.