Truncated Julian Day (TJD)

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Equation / Last modified by Administrator on 2015/10/23 01:05
`"TJD" = `
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MichaelBartmess.Truncated Julian Day (TJD)

This equation gives you the Truncated Julian Day (TJD) when you input a Gregorian (standard modern calendar date).

The TJD's starting point epoch is midnight on May 24, 1868.

"The Truncated Julian Date (TJD) as introduced by NASA/Goddard in 1979 as part of a parallel grouped binary time code (PB-5) "designed specifically, although not exclusively, for spacecraft applications." TJD was a 4-digit day count from MJD 40000, which was May 24, 1968, represented as a 14-bit binary number. Since this code was limited to four digits, TJD recycled to zero on MJD 50000, or October 10, 1995, "which gives a long ambiguity period of 27.4 years". (NASA codes PB-1—PB-4 used a 3-digit day-of-year count.) Only whole days are represented. Time of day is expressed by a count of seconds of a day, plus optional milliseconds, microseconds and nanoseconds in separate fields. Later PB-5J was introduced which increased the TJD field to 16 bits, allowing values up to 65535, which will occur in the year 2147. There are five digits recorded after TJD 9999.."1 


If you input January 1, 2000, this equation will return the Truncated Julian Day:  11544.0

If you input May 24, 1968, this equation will return the Truncated Julian Day: 0.0

See Also