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To: Savant who wrote (3002)	11/8/1998 3:30:00 PM
From: Apex	Respond to of 4201

Savvy: Got to see that damn Halley's comet another 105 times 'till Y10k...another 105 space ships and another 105 lunatics. o/c :-) Apex

To: Savant who wrote (3002)	11/8/1998 3:50:00 PM
From: Apex	Read Replies (1) \| Respond to of 4201

Gregorian calendar Description The Gregorian calendar is a modified version of the Julian calendar. The only difference being the specification of leap years. The Julian calendar specifies that every year that is a multiple of 4 will be a leap year. This leads to a year that is 365.25 days long, but the current accepted value for the tropical year is 365.242199 days. To correct this error in the length of the year and to bring the vernal equinox back to March 21, Pope Gregory XIII issued a papal bull declaring that Thursday October 4, 1582 would be followed by Friday October 15, 1582 and that centennial years would only be a leap year if they were a multiple of 400. This shortened the year by 3 days per 400 years, giving a year of 365.2425 days. Another recently proposed change in the leap year rule is to make years that are multiples of 4000 not a leap year, but this has never been officially accepted and this rule is not implemented in these algorithms. Valid Range 4714 B.C. to 9999 A.D. Although this software can handle dates all the way back to 4714 B.C., such use may not be meaningful. The Gregorian calendar was not instituted until October 15, 1582 (or October 5, 1582 in the Julian calendar). Some countries did not accept it until much later. For example, Britain converted in 1752, The USSR in 1918 and Greece in 1923. Most European countries used the Julian calendar prior to the Gregorian. Julian calendar Description Julias Ceasar created the calendar in 46 B.C. as a modified form of the old Roman republican calendar which was based on lunar cycles. The new Julian calendar set fixed lengths for the months, abandoning the lunar cycle. It also specified that there would be exactly 12 months per year and 365.25 days per year with every 4th year being a leap year. Note that the current accepted value for the tropical year is 365.242199 days, not 365.25. This lead to an 11 day shift in the calendar with respect to the seasons by the 16th century when the Gregorian calendar was created to replace the Julian calendar. The difference between the Julian and today's Gregorian calendar is that the Gregorian does not make centennial years leap years unless they are a multiple of 400, which leads to a year of 365.2425 days. In other words, in the Gregorian calendar, 1700, 1800 and 1900 are not leap years, but 2000 is. All centennial years are leap years in the Julian calendar. The details are unknown, but the lengths of the months were adjusted until they finally stablized in 8 A.D. with their current lengths: January 31 February 28/29 March 31 April 30 May 31 June 30 Quintilis/July 31 Sextilis/August 31 September 30 October 31 November 30 December 31 In the early days of the calendar, the days of the month were not numbered as we do today. The numbers ran backwards (decreasing) and were counted from the Ides (15th of the month - which in the old Roman republican lunar calendar would have been the full moon) or from the Nonae (9th day before the Ides) or from the beginning of the next month. In the early years, the beginning of the year varied, sometimes based on the ascension of rulers. It was not always the first of January. Also, today's epoch, 1 A.D. or the birth of Jesus Christ, did not come into use until several centuries later when Christianity became a dominant religion. Valid Range 4713 B.C. to 9999 A.D. Although this software can handle dates all the way back to 4713 B.C., such use may not be meaningful. The calendar was created in 46 B.C., but the details did not stabilize until at least 8 A.D., and perhaps as late at the 4th century. Also, the beginning of a year varied from one culture to another - not all accepted January as the first month.