EPHEMERIS TIME is an independent variable in the equation of the celestial bodies motion (differ from the universal time, determined by the Earth rotation and so non-uniformly, ephemeris time is the uniform time). The unit of ephemeris time is an ephemeris second equal to 1/31556925,9747 part of a tropic year for 1900 year, January 0, 12:00 of ephemeris time.

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