The Perpetual Calendar .... Introduction Page .... Frank's Humble Abode at frankosite2020.com .... formerly known as frankosport.com
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Introduction ... 1: Calendar Beginnings
The Julian Calendar was introduced in 45 B.C., and would remain in use through 1582 A.D. By that time, papal scholars had estimated that certain annual and seasonal celebrations, religious or other, were off by 10 days. Pope Gregory XIII issued an order that those 10 days be dropped, all at one time. So, the day immediately after Thursday October 4th, 1582 became Friday October 15th. In 1582, Julian Year Calendar #2 was used up to October 4th. Beginning October 15th and through to the end of 1582, Gregorian Year Calendar #6 would be used. | Click here for 1582 Calendar (opens in new window or tab) To keep the dates of annual and seasonal celebrations in sync, Pope Gregory decreed that only century years which were divisible by 400 (1600, 2000, 2400, etc) would be 366-day Leap Years. Century which were not divisible by 400 (1700, 1800, 1900, 2100, 2200, 2300, etc) would only be regular 365-day years. The change was adopted almost at once by most countries. However, the British Empire and American Colonies did not change over until September 2nd, 1752. Eleven days were dropped, making the next day September 14th. | Click here for 1752 Calendar (opens in new window or tab) Julian and Gregorian Systems both use 14 different Year Calendars -- seven 365-day regular year calendars (1-2-3-4-5-6-7) and seven 366-day leap year calendars (8-9-10-11-12-13-14). You can view each of these year calendars by clicking on any of the blue-colored numbers (01 thru 14) shown below. Year Calendars ... |
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Look up certain specific dates in the Gregorian Calendar era, such as the following ... A: September 10th in 1945, 2345 and 2745. C: October 15th in 1681, 2081, 2481 and 2881 B: July 4th in 1833, 2233 and 2633 D: December 25th in 1776, 2176, 2576 and 2976 Note that the day-of-the-week and specific year calendar used are always the same, as follows ... A: September 10th ... Monday / Year Calendar # 2 (1945, 2345 and 2745) B: October 15th ....... Wednesday / Year Calendar # 4 (1681, 2081, 2481 and 2881) C: July 4th ............... Thursday / Year Calendar # 3 (1833, 2233 and 2633) D: December 25th ... Wednesday / Year Calendar # 9 (1776, 2176, 2576 and 2976) Why do the Gregorian Calendar dates "always come back to square" so to speak every 400 years ?? Answer - A 400-year period such as Saturday January 1st 1600 through Friday December 31st 1999, breaks down like this ......
109,500 days .... 300 standard non-leap years x 365 days
+ 1,095 days .... Century Years 1700, 1800 and 1900,
which are not divisible by 400 (365 days x 3)
+ 35,136 days .... 96 standard Leap Years x 366 days
Years XX04 thru XX96, each century
+ 366 days .... Century Year 1600, which is divisible by 400
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146,097 total days from 1600 to 1999 -OR- exactly 20,871 7-day weeks
SO .. January 1st, 2000 is on .. Saturday !! You can "guess the rest".
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