This picture is the equation of time plotted over one year -- Julian Year 2000. The vertical scale is minutes difference between local and mean solar noon over the span of one year. This curve appears periodic, but its maxima and minima slowly change due to the Precession of the Equinoxes. In the year 1246, when the Earth-Sun Perigee coincided with the Winter Solstice, the curve was exactly symmetrical about the Winter Solstice. This won't happen again until approximately the year 27246.