Editing Barycentric Dynamical Time (section)

==Definition==

IAU resolution 3 of 2006<ref>[http://www.iau.org/static/resolutions/IAU2006_Resol3.pdf IAU 2006 resolution 3]</ref> defines TDB as a linear transformation of [[Barycentric Coordinate Time|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.<ref name=timgraf>{{cite journal |last1=Seidelmann |first1=P. K. |last2=Fukushima |first2=T. |title=Why new time scales? |journal=Astronomy and Astrophysics |date=1992 |volume=265 |issue=2 |page=835 |bibcode=1992A&A...265..833S}}</ref> As of the beginning of 2011, the difference between TDB and TCB is about 16.6 seconds.

:TDB = TCB − L{{sub|B}}×(JD{{sub|TCB}} − T{{sub|0}})×86400 + TDB{{sub|0}}

where L{{sub|B}} = 1.550519768{{E|−8}}, TDB{{sub|0}} = −6.55{{E|−5}} s, T{{sub|0}} = 2443144.5003725, and JD{{sub|TCB}} is the TCB [[Julian day|Julian date]] (that is, a quantity which was equal to T{{sub|0}} on 1977 January 1 00:00:00 [[International Atomic Time|TAI]] at the geocenter and which increases by one every 86400 seconds of TCB).