EquationOfTime

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Chart for this topic: Equation of Time and Moon Distance.cht

EquationOfTime (Date)

Parameters:

Date Variable = Date (cannot be changed)

The Equation of Time indicator returns the difference between solar time (as measured by a sundial) and mean clock time. It assumes that measurements are taken in the middle of a time zone and that there is no daylight savings time in effect. The solar and clock times are different due to combination of two factors:

(a)	Obliquity of the ecliptic - Earth’s axis of rotation is tilted at about 23 degrees to the perpendicular to the plane of the Earth’s orbit around the Sun, and

(b)	Eccentricity of Earth’s orbit - Earth’s orbit around the Sun is not a circle but rather an ellipse.

Maximum disparity between solar and clock time happens in early November when apparent solar time is ahead of the mean clock time by more than 16 minutes. In mid-February solar time is actually behind clock time by about 14 minutes.

The indicator output is in minutes.

See References for more information.