Definition
IAU resolution 3 of 2006 defines TDB as a linear transformation of TCB. TCB diverges from both TDB and TT. TCB progresses faster at a differential rate of about 0.5 second/year, while TDB and TT remain close. As of the beginning of 2011, the difference between TDB and TCB is about 16.6 seconds.
- TDB = TCB − LB×(JDTCB − T0)×86400 + TDB0
where LB = 1.550519768×10−8, TDB0 = −6.55×10−5 s, T0 = 2443144.5003725, and JDTCB is the TCB Julian date (that is, a quantity which was equal to T0 on 1977 January 1 00:00:00 TAI at the geocenter and which increases by one every 86400 seconds of TCB).
Read more about this topic: Barycentric Dynamical Time
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