corrective measures

[Rives McDow <rmcdow@xxxxxxxxxxx>]

Title: corrective measures

Earlier I made a post that was misinterpreted.  Here is a correcting bit.

    I wasn't proposing to convert to the Julian Calendar, but to the julian day count.  This use of a name that is so similar to an existing calendar system has caused a lot of confusion, but there is no relationship at all between the two methods.  The julian day count was proposed by the astronomer Scallinger in some former century, after running into problems converting back and forth between ancient calendar systems to pin down astronomical events.   Scallinger picked a calendrical conjunction that predated all the calendar systems in history with the exception, I believe of the Mayan calendar.  This date was Gregorian 4713 BC Jan. 1, I believe.  I am travelling right now, and my references are at home, along with all my source and header files.  Today is julian Day 2451581, or 2451582.1717 right now to be exact, as the day is usually expressed as a float referenced to Greenwich.  The modified julian date, used by Nasa and others not wanting or having space for such a large number in their memory map or processor capabilities, is the julian day minus 2,400,000.  Today's modified julian day is 51581.  Either works, as the other can be derived by simple subtraction or addition.  Here is a url that has a pretty good overview of today's date in various calendar systems.  

http://www.ecben.net/calendar.shtml

    This can seem a little overwhelming when first considering the coding.  However, I have found that calendar systems are solar, lunar, or solar/lunar, and that the differences are primarily the setting of the epoch, with a few exceptions (Hebrew being one).  Converting back and forth between the julian day count and any calendar system is fairly straightforward, using the proper algorithm.  I reference the julian day count to the west side of the International Date Line, for reasons stated earlier.  This has proved to be the best approach in the applications I have developed so far, but I am open to arguments.

Sincerely,


Rives McDow