The term ephemeris time (often abbreviated ET) can in principle refer to time in association with any ephemeris (itinerary of the trajectory of an astronomical...

celestial navigation, an ephemeris (/ɪˈfɛmərəs/; pl. ephemerides /ˌɛfəˈmɛrədiːz/; from Latin ephemeris 'diary', and Greek ἐφημερίς (ephemeris) 'diary, journal')...

transition, newly established, with the ephemeris second. The ephemeris second is a unit in the system of time that, when used as the independent variable...

time standards such as sidereal time and ephemeris time, for most practical purposes, by newer time standards based wholly or partly on atomic time using...

Supplement to the Astronomical Ephemeris and the American Ephemeris and Nautical Almanac, p. 9, ... defined ephemeris time ... [was] adopted by the International...

century. Time standards based on Earth rotation were replaced (or initially supplemented) for astronomical use from 1952 onwards by an ephemeris time standard...

third release of the JPL Ephemeris Tapes, and was a special purpose, short-duration ephemeris. The then-current JPL Export Ephemeris was DE19. These early...

(non-relativistic) former standard of ephemeris time (adopted by the IAU in 1952 and superseded 1976). In 2006, after a history of multiple time-scale definitions and...

ephemeris second (see Ephemeris time - redefinition of the second). In 1976, however, the IAU resolved that the theoretical basis for ephemeris time was...

In this role, TT continues Terrestrial Dynamical Time (TDT or TD), which succeeded ephemeris time (ET). TT shares the original purpose for which ET was...