Well, I started to join in in the EoT calculation fun, following Francois Blateyron's original question. I began by implementing his equations in a spreadsheet, as he did. I used Microsoft Excel...
With Robert Sinnott's correction to the longitude of perihelion calculation, I was getting a close fit, but still not quite "on". Today, I started to implement Paolo Gregorio's posting of the algorithm from the Explanatory Supplement. Well, heck, all I need do is add the necessary offset to Excel's intrinsic date function (based on 1/1/1900 = 0), and I have Julian Date. Piece of cake. Right. Until I notice a one day difference from (Excel) calculated JDate to that from The Dialist's Companion by Bob Terwilliger and fred Sawyer of NASS. Not to be stopped, I grabbed an old copy of the BASIC algorithm from Sky and Telescope's Astronomical Computing (May 1984), and coded that in Excel Visual BASIC. Well, *that* date agrees with the Dialist, so what's wrong with Excel?? A little troubleshooting led to the hitherto unknown fact that 1900 really *was* a leap year. At least according to Excel! Is this a known bug? Certainly something to be aware of, anyway! Not to mention that the date computations only support the range of 1/1/1900 <= D <= 12/31/2078... Dave Bell
