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Re: Julian Date formula for sun algorithm
From: Alexandre Eremenko
Date: 2025 Sep 8, 11:51 -0700
From: Alexandre Eremenko
Date: 2025 Sep 8, 11:51 -0700
I copy the algorithm from the book of Meus Astronomical Algorithms.
Input: Y=the year, M=the month (1 to 12) D=the day (and time). For example D=4.5417 for day four, 1pm.
1. If M>2 leave Y and M unchanged. If M=1 or 2 replace Y by Y-1 and M by M+12.
2. A:=INT(Y/100), and B:=2-A+INT(A/4)
3. JD=INT(365.25(Y+4716))+INT(30.6001(M+1))+D+B-1524.5
Example: I am writing this message on 9/8/2025 at 3:30pm.
So Y=2025, M=9, D=8.645833, A=20, B=2-20+5=-13.
JD=2460927.1
(Computed with my Casio fx-250D)
Alex.
