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Dynamic Time
The family of time scales introduced in 1984 to replace ephemeris time. |
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Eccentricity
A measure of the degree of departure of an ellipse from the shape of a circle expressed as a ratio of the distance of the focus from the center to the semi-major axis. |
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Ecclesiastical
Refers to calendric matters which concern, or originate with, church authority and not civil authority. Distinguished from civil. |
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Ecliptic
The plane containing the orbit of the Earth around the Sun. |
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Embolismic
Generally, a synonym for intercalary. The term is typically applied to years, in which context it means "leap." |
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Epact
Historically, this term has several meanings. One rare meaning is any intercalated day. Two others are related. One is the number of days by which the solar year exceeds a lunar year of 12 months; the other means the number of days of the moon's age on the first day of the year. It is this latter definition that occurs most frequently in discussions of calendric algorithms. |
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Epagomena
As used in SCDTL, the term means days inserted at the end of a year, as opposed to intercalary which means days inserted within the year. |
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Ephemeris
From the Greek ephemeros, meaning daily. A table of calculated positions (or other data) for a series of instants normally given at equal intervals for a given celestial body. |
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Ephemeris day
A period of time equal to 86,400 seconds in the uniform Dynamic Time scale. |
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Ephemeris Time (ET)
A time scale used by astronomers and derived from analyses of lunar motion. Replaced by TDT in 1984. |
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Epoch
A particular moment in time used as a reference point from which elapsed time is measured. |
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Equation of time
The difference between mean solar time and real solar time. |
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Equinoctial hours
From the Latin, horae equinoctales. Hours of uniform duration, which do not vary in length with the season. Distinguished from temporal hours, to which they are equal at the time of the vernal equinox. |
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