(12C) Gregorian Date to Julian Day Number and vice versa

[Albert Chan]

(01-14-2019 09:28 PM)Thomas Klemm Wrote:  But I have to admit that I still don't really understand the difference between Julian Date and Julian Day Number.

Based on Astronomy Answers: Julian Day Number
Chronological Julian Date assumed timer started at 00:00:00 LT, instead of 12:00:00 UTC

For Jan 1, 2000, 00:00:00 UTC, time zone TZ = +6 hrs = 0.25 day

JDN = floor(JD) = floor(2451544.5) = 2451544
CJDN = floor(CJD) = floor(JD + TZ + 0.5) = 2451545

If true, what post #1 calculated is actually Chronological Julian Day Number.