IAU(1991) RECOMMENDATION V
Use of Barycentric Dynamical Time (TDB)
The XXIst General Assembly of the International Astronomical Union,
that important work has already been performed using Barycentric Dynamical Time (TDB), defined by IAU Recommendation 5 (1976) of IAU Commissions 4, 8 and 31, and Recommendation 5 (1979) of IAU Commissions 4, 19 and 31,
that where discontinuity with previous work is deemed to be undesirable, TDB may be used.
Note to Recommendation V
Some astronomical constants and quantities have different numerical values depending upon the use of TDB or TCB. When giving these values, the time scale used must be specified.