TJD = MJD - 40000 = JD - 2440000.5
(TJD : Truncated Julian Day; MJD : Modified Julian Day; JD : Julian Day Number *, starts at 12:00 noon UT;
see COM-TN-SYS-DAT-004, 1989-02-14)
* The Julian Date (JD) is the interval of time in days and fraction of
a day since 4713 B.C. January 1, Greenwich noon.
The Julian Day Number (also JD) is the integral part of the Julian Date.