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RE: Kill Time At Work With Recreational Math: Calculate Sunset and Sunrise Times
That's interesting that you had to adjust your JD by 0.5 day. That means your M could be off as well, but the error of 0.5 of a day in that calculation would only amount to about 2 minutes difference in sunset and sunrise.
Thanks. I found the problem: I had originally set the Western calendar date in cell C9 to start at 12 noon in order to emulate the Julian calendar pattern of starting the day at noon. I should not have done that.
The equation in cell C21 for J_transit also does this. I guess the person developing the system of equations was already compensating for this.
So there was a double compensation for the Julian calendar quirkiness of starting the day at noon which gave me the error of being off by 12 hours.
I have now adjusted cell C9 to start at midnight (12:00:01 am) and set cell C21 back to the form of the equation in Wikipedia and everything works.