Mean solar time Mean solar time is the time shown on ordinary clocks and watches – the time that is used for daily living. It assumes that the earth moves at a uniform rate around the sun, an average day of 24 hours. The earth actually makes one perfect rotation on its axis in relation to the stars in 23 hours, 56 minutes and 4.09 seconds. Since the invention of the pendulum, clocks have been set for the mean solar time using the adjusted 24-hour day.
