Dar- Thursday, April 15, 2004, 1:33:56 PM, you wrote:
DS> Uh, I mean URLs that give me confidence that there really is such thing DS> as Julian day. I guess I can look those up myself; I have some info on DS> Julian day as astronomers use it. Like this? From the Time FAQ for sci.astro: What's a Julian date? It's the number of days since noon 4713 BC January 1. What's so special about this date? Joseph Justus Scaliger (1540--1609) was a noted Italian-French philologist and historian who was interested in chronology and reconciling the dates in historical documents. Before the western civil calendar was adopted by most countries, each little city or principality reckoned dates in its own fashion, using descriptions like "the 5th year of the Great Poo-bah Magnaminus." Scaliger wanted to make sense out of these disparate references so he invented his own era and reckoned dates by counting days. He started with 4713 BC January 1 because that was when solar cycle of 28 years (when the days of the week and the days of the month in the Julian calendar coincide again), the Metonic cycle of 19 years (because 19 solar years are roughly equal to 235 lunar months) and the Roman indiction of 15 years (decreed by the Emperor Constantine) all coincide. There was no recorded history as old as 4713 BC known in Scaliger's day, so it had the advantage of avoiding negative dates. Joseph Justus's father was Julius Caesar Scaliger, which might be why he called it the Julian Cycle. Astronomers adopted the Julian Cycle to avoid having to remember "30 days hath September ...." For reference, noon on 1995 October 9 was Julian day 2450000. Note that this has nothing to do with the Julian calendar: The Julian calendar, instituted by Julius Caesar (who else?), has a 365-day ordinary year with a 366-day leap year every fourth year. This gives a mean year length of 365.25 days, not a very large error. However, the error builds up, and by the sixteenth century, reform was considered desirable. A new calendar was established in most Roman Catholic countries in 1582 under the authority of Pope Gregory XIII; in that year, the date October 4 was followed by October 15 -- a correction of 10 days. Most non-Catholic countries adopted this "Gregorian" calendar somewhat later (Great Britain and the American colonies in 1752), and by then the difference between Julian and Gregorian dates was even greater than 10 days. (Russia didn't adopt the Gregorian calendar until after the "October Revolution" -- which took place in November under the new calendar!) Many of the calendar changeovers elicited strong emotional reactions from the populations involved; people objected to "losing ten (or more) days of our lives". -- -Mark Wieder [EMAIL PROTECTED] _______________________________________________ use-revolution mailing list [EMAIL PROTECTED] http://lists.runrev.com/mailman/listinfo/use-revolution