When I teach chemistry, one of my early topics is the difference between precision and accuracy. On one quiz, I asked: "You measure the length of your nose. The readout is 3.12486 meters. Is this answer precise? Is this answer accurate?" One of my students answered, "It's accurate if your name is Pinnochio." That's a perfect answer -- it shows mastery of the concept, and a sense of humor. Time is not prone to such deep understanding.
But my new, magical watch has one flaw. I can't set it 5 minutes fast. NowI have to learn to be on time all over again.