The equation of time

This is the equation that explains the difference between mean and apparent solar time. The time between successive transits of the Sun across the meridianis called the mean solar day. However true noon will only coincide with mean noon atcertain times of the year. This is because the Earth does not travel at a uniform speed as it orbits the Sun due to the eccentricity of its orbit.
Solar time is not of continuous length. The length of a solar day varies due to:
(a) the fact that the Earth goes round the Sun in an ellipse and so moves at different speeds at different times of the year
(b) the Earth's axis is inclined at 23.5^o to the plane of the orbit

Date	Minutes		Date	Minutes
January 1	-3.2		July 1	-3.5
January 16	-9.6		July 16	-5.9
February 1	-13.5		August 1	-6.3
February 16	-14.2		August 16	-4.4
March 1	-12.6		September 1	-0.2
March 16	-9.0		September 16	+4.8
April 1	-4.2		October 1	+10.0
April 16	-0.0		October 16	+14.2
May 1	+2.8		November 1	+16.3
May 16	+3.7		November 16	+15.3
June 1	+2.4		December 1	+11.3
June 16	-0.4		December 16	+4.8