See any year calendar (from 1 AD to infinity). We follow the catholic world rules. Therefore, you'll see in the year 1582, the transition year from Julian to Gregorian Calendar, we didn't have the days 5 to 14 in October month:
Note: If you compare this calendar with the one in Microsoft/Office/Excel, you will find a difference in year 1900. This is a problem in Excel, that incorrectly considers 1900 a leap year.
The world smallest perpetual calendar!
Know the world smallest (and the unique) pocket perpetual calendar from 1 AD to infinity, going to the drawing page. Print it, cut out and follow the assembly instructions.
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Which day of the week was 29 April 1977? Arch (A) under thousand/hundred 19 (B). APR (C) under ten/unit 77 (D). April 1977, 29 (E) was Friday (F). |
Thousand/hundred 15J (Julian calendar) is used only until 4 Oct 1582 and 15G (Gregorian calendar) is used only from 15 Oct 1582.
Match leap YEAR and JAN or FEB months (inside rectangles). Note that 1700, 1800, 1900, 2100 and 2200 are not leap years, although divisible by 4.
Note that APR, JUN, SEP and NOV have only 30 days and FEB 28/29 days.
The device can be used for other centuries: 19XX is good for 23XX, 27XX, 31XX etc. and 20XX is good for 24XX, 28XX, 32XX etc. etc. Everything repeats each 4 centuries.
You can use my pocket perpetual calendar in other situations, like in the United Kingdom, where the "missing" days were the 3rd to the 13th September 1752. Just take in account that 16J thousand/hundred would be on the "02 09 18 22" sector and 17J thousand/hundred (until 2/9/1752) would be on the "03 10" sector (while the gregorian calendar has a periodicity of 4 centuries, the julian calendar has a periodicity of 7 centuries). You'll see the 2nd September 1752 (julian calendar) was Wednesday and the 14th September 1752 (gregorian calendar) was Thursday.
Also see other samples of pocket perpetual calendars, if you are an inquisitive person.
A bit of History...
The Julian Calendar began on the 46th year b.C. and ended theoretically on 4 October 1582. And the Gregorian Calendar began on 15 of the same month, "erasing" from history the days from 5 to 14 October. Portugal and its colonies adopted the Gregorian reform at its beginning, but many nations, including England, did not. Thus, in the English-speaking world, the "missing" days were the 3rd to the 13th September 1752.
Leap years
Although in the Julian Calendar every year that is divisible by 4 is a leap year, the Gregorian Calendar, for greater astronomical precision, provides that years divisible by 4 are leap years, except those ending in "00" and not divisible by 400. That is, the years 1584, 1588... 1600, 2000, 2400 etc. are leap years, but not 1700, 1800, 1900, 2100 etc.. Just because tropic year isn't exactly 365 days and a quarter lasting.
A timely reminder
The 21st century and the 3rd millenium began on 1st January 2001, not 2000.
