What is the precise definition of JDE's Julian Date format?

Question

I am writing code to convert from a Gregorian date to a JDE (J.D.Edwards) Julian date.

Note: a JDE Julian date is different from the normal usag

Answer 1

Wow, there's a lot of complicated code in some of these answers just to convert to and from JDE julian dates. There are simple ways in Excel and VBA to get there.

FROM JULIAN

Excel (assuming julian date is in A1):

=DATE(1900+LEFT(A1,LEN(A1)-3),1,RIGHT(A1,3))

VBA (from julian date, j, stored as String):

d = DateSerial(1900 + Left$(j, Len(j) - 3), 1, Right$(j, 3))

VBA (from julian date, j, stored as Long):

d = DateSerial(1900 + Left$(j, Len(CStr(j)) - 3), 1, Right$(j, 3))

TO JULIAN

Excel (assuming date is in A1):

=(YEAR(A1)-1900)*1000+A1-DATE(YEAR(A1),1,0)

VBA (to a Long, j):

j = (Year(d) - 1900) * 1000 + DatePart("y", d)

Answer 2

Update: Sorry, JDE is probably something else. But for reference:

The JDE I know is different. From page 59 in the book "Astronomical algorithms" (Jean Meeus, ISBN 0-943396-35-2):

"If the JD corresponds to an instant measured in the scale of Dynamical Time (or Ephemeris Time), the expression Julian Ephemeris Day (JDE) is generally used. (Not JED as
it is sometimes written. The 'E' is a sort of index appended to 'JD')"

JD and JDE (for the same point in time) are close in value as the difference UT and ET is on the order of minutes. E.g. ET-UT was 56.86 seconds in 1990 and -2.72 seconds in 1900.

There is also MJD (Modified Julian Day):

MJD = JD - 2400000.5

Zero point for MJD is 1858-11-17, 0h UT.

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Note that JD as Julian date is a misnomer. It is Julian day. The JD has nothing to do with the Julian calendar. (This is in disagreement with the Wikipedia article, this is from the author of the book mentioned above, Jean Meeus - a Belgian astronomer specializing in celestial mechanics.)