text: Partly in acknowledgement of the widespread use of Teph via the JPL ephemerides, IAU resolution 3 of 2006 (re-)defined Barycentric Dynamical Time (TDB) as a current standard. As re-defined in 2006, TDB is a linear transformation of TCB. The same IAU resolution also stated (in note 4) that the "independent time argument of the JPL ephemeris DE405, which is called Teph" (here the IAU source cites), "is for practical purposes the same as TDB defined in this Resolution". Thus the new TDB, like Teph, is essentially a more refined continuation of the older ephemeris time ET and (apart from the  periodic fluctuations) has the same mean rate as that established for ET in the 1950s.
  Use in official almanacs and ephemerides
  Ephemeris time based on the standard adopted in 1952 was introduced into the Astronomical Ephemeris (UK) and the American Ephemeris and Nautical Almanac, replacing UT in the main ephemerides in the issues for 1960 and after.  (But the ephemerides in the Nautical Almanac, by then a separate publication for the use of navigators, continued to be expressed in terms of UT.)  The ephemerides continued on this basis through 1983 (with some changes due to adoption of improved values of astronomical constants), after which, for 1984 onwards, they adopted the JPL ephemerides.
  Previous to the 1960 change, the 'Improved Lunar Ephemeris' had already been made available in terms of ephemeris time for the years 1952—1959 (computed by W J Eckert from Brown's theory with modifications recommended by Clemence (1948)).