Before the Gregorian calendar, most countries relied on the Julian calendar, which was introduced by Julius Caesar in 45 BC. It was in common use until the 1500s. The Julian calendar creates an error of 1 day every 128 years.
The Gregorian calendar was proposed by Aloysius Lilius, a physician from Naples, and adopted by Pope Gregory XIII in accordance with the instructions from the Council of Trent (1545-1563) to correct for errors in the older Julian calendar. It was decreed by Pope Gregory XIII in a papal bull on February 24 1582. This bull was named “Inter Gravissimas” after its first two words.
It took time to switch to the new calendar. The following list contains the dates for changes in a number of different countries:
Albania: December 1912
Austria: Different regions on different dates.
Brixen, Salzburg and Tyrol: 5 Oct 1583 was followed by 16 Oct 1583
Carinthia and Styria: 14 Dec 1583 was followed by 25 Dec 1583
See also Czechoslovakia and Hungary
Belgium: See the Netherlands
Bulgaria: 31 Mar 1916 was followed by 14 Apr 1916
Canada: Different areas changed at different times.
Newfoundland and Hudson Bay coast: 2 Sep 1752 was followed by 14 Sep 1752
Mainland Nova Scotia: Gregorian 1605 - 13 Oct 1710
Julian 2 Oct 1710 - 2 Sep 1752
Gregorian since 14 Sep 1752
Rest of Canada: Gregorian from first European settlement
China: The Gregorian calendar replaced the Chinese calendar in 1912, but the Gregorian calendar
was not used throughout the country until the communist revolution of 1949.
Czechoslovakia (i.e. Bohemia and Moravia): 6 Jan 1584 was followed by 17 Jan 1584
Denmark (including Norway): 18 Feb 1700 was followed by 1 Mar 1700
Estonia: 31 Jan 1918 was followed by 14 Feb 1918
Finland: Then part of Sweden. (Note, however, that Finland later became part of Russia, which
then still used the Julian calendar. The Gregorian calendar remained official in Finland, but
some use of the Julian calendar was made.)
France: 9 Dec 1582 was followed by 20 Dec 1582
Alsace: 5 Feb 1682 was followed by 16 Feb 1682
Lorraine: 16 Feb 1760 was followed by 28 Feb 1760
Strasbourg: February 1682
Germany: Different states on different dates.
Catholic states on various dates in 1583-1585
Prussia: 22 Aug 1610 was followed by 2 Sep 1610
Protestant states: 18 Feb 1700 was followed by 1 Mar 1700
(Many local variations)
Great Britain and Dominions: 2 Sep 1752 was followed by 14 Sep 1752
Greece: 9 Mar 1924 was followed by 23 Mar 1924 (Some sources say 1916 and 1920)
Hungary: 21 Oct 1587 was followed by 1 Nov 1587
Ireland: See Great Britain
Italy: 4 Oct 1582 was followed by 15 Oct 1582
Japan: The Gregorian calendar was introduced to supplement the traditional Japanese calendar
on 1 Jan 1873.
Latvia: During German occupation 1915 to 1918
Luxemburg: 14 Dec 1582 was followed by 25 Dec 1582
Netherlands (including Belgium):
Zeeland, Brabrant, and the “Staten Generaal”: 14 Dec 1582 was followed by 25 Dec 1582
Holland: 1 Jan 1583 was followed by 12 Jan 1583
Limburg and the southern provinces (currently Belgium): 20 Dec 1582 was followed by 31 Dec 1582
Or 21 Dec 1582 was followed by 1 Jan 1583
Groningen: 10 Feb 1583 was followed by 21 Feb 1583
Went back to Julian in the summer of 1594
31 Dec 1700 was followed by 12 Jan 1701
Gelderland: 30 Jun 1700 was followed by 12 Jul 1700
Utrecht and Overijssel: 30 Nov 1700 was followed by 12 Dec 1700
Friesland: 31 Dec 1700 was followed by 12 Jan 1701
Drenthe: 30 Apr 1701 was followed by 12 May 1701
Norway: Then part of Denmark.
Poland: 4 Oct 1582 was followed by 15 Oct 1582
Portugal: 4 Oct 1582 was followed by 15 Oct 1582
Romania: 31 Mar 1919 was followed by 14 Apr 1919 (The Greek Orthodox parts of the country may have changed later)
Russia: 31 Jan 1918 was followed by 14 Feb 1918 (In the eastern parts of the country the change may not have occurred until 1920)
Scotland: Much confusion exists regarding Scotland’s change. Different authorities disagree about
whether Scotland changed together with the rest of Great Britain, or if they had changed earlier.
Spain: 4 Oct 1582 was followed by 15 Oct 1582
Sweden (including Finland): 17 Feb 1753 was followed by 1 Mar 1753
Switzerland: Catholic cantons: 1583, 1584 or 1597
Protestant cantons: 31 Dec 1700 was followed by 12 Jan 1701 (Many local variations)
Turkey: Gregorian calendar introduced 1 Jan 1927
USA: Different areas changed at different times.
Along the Eastern seaboard: With Great Britain in 1752.
Mississippi valley: With France in 1582.
Texas, Florida, California, Nevada, Arizona, New Mexico: With Spain in 1582
Washington, Oregon: With Britain in 1752.
Alaska: October 1867 when Alaska became part of the USA.
Wales: See Great Britain
Because of this transition, the Gregorian calendar will not calculate dates that are consistent with the Julian calendar prior to the date that Gregorian calendar was introduced.
The Julian and later the Gregorian calendars were designed to reflect the motion of the earth around the sun. The year is the actual length of time it takes for the Earth to complete one orbit around the Sun. The Gregorian calendar has a regular years = 365 days and a leap years = 366 days. The leap year (29 days in February) has one more day than a regular year (28 days in February).
Leap year rules:
For people in the northern hemisphere:
For people in southern hemisphere these events are shifted half a year.
The Gregorian calendar today serves as an international standard for civil use, and NaturCalendar™ is based on the Gregorian calendar.
“Frequently Asked Questions about Calendars”, Claus Tøndering, 28 October 2001, Copyright ©2001 by Claus Tøndering.
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