What is a solar day?
A solar day has been defined as the elapsed time frame it takes for the sun to reach it’s highest point in the sky twice, i.e. from noon to noon. Because the Earth is in motion on its orbit around the Sun in the course of a day, the Earth must turn about 4 minutes longer each day (3 minutes and 56 seconds, to be exact) to bring the Sun back to that point. That’s why “clock time” doesn’t quite correspond to solar time.
