The discussion of Rotation Period and Day Length presumes that the motion of the planets around the Sun is more or less uniform. Because Mars' orbit has an eccentricity of nearly 10%, its angular motion around the Sun varies by as much as 20%, which can alter the difference between the length of its day and the length of its rotation period, normally around 2 minutes and 12 seconds, by about half a minute. This means that in a week or so at certain times of the year a uniform clock will run several minutes ahead or behind the rotation of the planet. The effect is similar to the one which makes sundials run "fast" or "slow" on the Earth, but is considerably more exaggerated. (The affect on Earth sundials is referred to as The Equation of Time, and is often shown on globes with a figure-8-like feature called an analemma.)