How does a sundial work?

Indeed, sir, a sundial works by using the position of the sun in the sky to tell the time. The key component is the gnomon, the part that casts a shadow. As the sun moves across the sky during the day, the shadow shifts on a marked surface called the dial plate. The markings on this plate are calibrated so that each position of the shadow corresponds to a specific hour. By reading where the shadow falls, one can determine the time with remarkable accuracy, provided the sundial is properly aligned with true north and the sun is shining.