Passage I

Solar time is determined by the position of the Sun relative to a meridian (an imaginary line that passes through the northernmost and southernmost points of the horizon, dividing the visible sky into 2 equal halves). At solar noon, the Sun appears to cross the meridian. A solar day is the period between one solar noon and the next. Because the Sun’s apparent motion is not uniform, a solar day is generally not the same length as a mean day, which is exactly 24 hrs (1,440 min). See Figure 1.

Figure 2 shows how the difference between solar time and mean time (time as indicated by a clock) varies throughout the year.