Julian and Gregorian Calendars

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Background

The most-used calendar in the modern world today is the Gregorian Calendar, named after Pope Gregory. It is based on a standard year of 365 days with modifications to keep it consistent with the earth’s movement around the sun. Though not perfect, the Gregorian Calendar will take 3300 years before being one day off.

The previous calendar in Europe was the Julian Calendar, instituted in 46 BC and named after Julius Caesar. The old Julian Calendar assumed the earth went around the sun in exactly 365.25 days. For this calendar to follow the earth’s movement, this rule was used - every year that was divisible by 4 was made a leap year of 366 days, otherwise it was a standard year of 365 days. In actual fact, the earth travels around the sun in 365.2422 days, about 11 minutes shorter than the old Julian Calendar. This discrepancy accumulated about 3 days short every 4 centuries. By 1582, the calendar was 10 days early.

The Catholic Church was very concerned because the celebration of Easter was figured from the spring equinox. And the spring equinox was now happening 10 days earlier than it should. As a result, on 24 February 1582 Pope Gregory XIII issued a decree (a papal bull) instituting a new calendar.

To return the spring equinox to 21 March, the new Gregorian Calendar chopped 10 days from the year. Also, a change already in progress was validated - the first day of the year was changed from the 25 March to 1 January. But most importantly, to keep consistent with the earth’s movement around the sun, a new rule was followed - every year that is exactly divisible by four is a leap year, except for centurial years that are not divisible by 400. This means that the year 2000, being exactly divisible by 400, was a leap year, but 2100, 2200, and 2300, although falling in the 4-year cycle, are not leap years because they are not evenly divisible by 400.

The Pope could not mandate these changes, only make the proposal. Some countries (mostly Catholic) adopted the Gregorian Calendar soon after the Pope issued the decree. Other countries (mostly Protestant) ignored the Pope and continued with their own calendars. But gradually the advantages became apparent and most countries adopted the Gregorian Calendar (first European countries and later other countries around the world).

The British Empire changed to the Gregorian Calendar in 1752. Because of these changes, there is some uncertainty for the dates between 1 January and 25 March in the years from 1582 until 1752 in the old British Empire. To avoid any confusion, write the date with both years' numbers. For example - 14 February 1699/1700. At the time it would have been considered 1699 according to the Julian Calendar, then in effect. But now it would be considered 1700 according to the Gregorian Calendar. Using the double-year dating and understanding its purpose can be helpful in recording historical events.

Julian to Gregorian calendar changes by country or region

The following list attempts to give the year of conversion from the Julian to the Gregorian calendar for many countries and their constituent states, where necessary. Some countries converted early and in their entirety, whereas other countries, such as Switzerland, The Netherlands, and Germany had provinces/cantons that converted at different times. This is because these countries have both Catholic and Protestant areas. Catholics adopted the Gregorian calendar very early, whereas most Protestant areas did not. An attempt has been made to list the conversion years of all constituent states, but this has not been possible in each case, as some states are absent from all the lists of works consulted.

This list has been compiled from various sources (see the list of works consulted at the bottom of the page). The reader will notice that there are sometimes more than one date for conversion for one particular jurisdiction. This is due to several factors. First, sometimes the sources do not agree and most do not give sources. In such cases, it might be impossible to determine the correct date of conversion. Second, a jurisdiction may have made a conversion when the Julian date ended at the end of a year and the Gregorian date took effect in the new year. Some sources list the previous year as the year of conversion, whereas others list the new year as the year of conversion. Third, parts of some jurisdictions may have converted, whereas other parts may have converted later. This is particularly true in Switzerland. Finally, a jurisdiction may have converted to the Gregorian, then back the Julian, then back to the Gregorian (e.g. Groningen). In such cases, the researcher is advised to consult all the sources listed below.

Year of adoption of the Gregorian Calendar. This means that the year given is the beginning year that the country/province/canton began using the Gregorian calendar and when you should start using the Gregorian feast day converter. Before that year, use the Julian converter. For example, Albania used the Julian calendar until 1912, when it switched to the Gregorian. It should be noted that this chart lists only the year, not the date, of conversion. For the exact date (which will be important!), the researcher is again advised to consult the sources listed below.[1][2][3][4][5][6][7][8]


Country Start numbered year
on 1 January
Adoption of
Gregorian Calendar
Albania 1912
Alsace (Elsaß) 1648, 1682
Lorraine 1579 1682
Austria (Österreich) 1583
Belgium 1582
Belgium, Liege (Liuk) 1583
Bohemia (Böhmen) 1584
Great Britian, British Empire 1752
Bulgaria 1916
China 1912
Czechoslovakia 1584
Denmark and Norway Gradual change from
13th to 16th centuries[9]
1700
Dutch Republic 1583 from 1582
Estonia 1918
Egypt 1875
Finland 1753
France 1564[10] 1582
France, Alsace 1648, 1682
France, Strasbourg 1648, 1682
France, Lorraine 1648, 1682
Germany, Catholic States 1583 or 1584
Germany, Aachen 1583
Germany, Alsace (Elsaß) 1648, 1682
Germany, Augsburg 1583, 1583
Germany, Baden 1583
Germany, Baden-Durlach 1700
Germany, Bavaria (Bayern) 1582, 1583
Germany, Brandenburg 1699
Germany, Cleve 1583
Germany, Cologne (Köln) 1583
Germany, Eichstadt 1583
Germany, Freiburg 1584
Germany, Freising 1583
Germany, Hannover (kingdom) 1700
Germany, Hennegau 1583
Germany, Hesse (Hessen) 1699
Germany, Hildesheim 1631
Germany, Julich 1583
Germany, Kurland 1617
Germany, Lausitz 1584
Germany, Lorraine (Lothringen) 1682, 1760
Germany, Mainz 1583
Germany, Minden 1630, 1668
Germany, Munster (Münster) 1583
Germany, Neuburg Palatinate (Pfalz) 1615
Germany, Nuremburg (Nürnberg) 1699
Germany, Osnabruck (Osnabrück) 1624
Germany, Paderborn 1585
Germany, Passau 1583
Germany, Prussia (Preußen) 1610, 1612, 1700
Germany, Regensburg 1583
Germany, Rhenish Palatinate (Pfalz) 1699
Germany, Saxony (Sachsen) 1699
Germany, Silesia (Schlesien) 1584
Germany, Strasbourg bisopric 1583
Germany, Strasbourg city 1682
Germany, Trier 1583
Germany, Ulm 1699
Germany, Westphalia (Westfalen) 1584
Germany, Wurzburg (Würzburg) 1583
Greece 1923
Britain and
British Empire
except Scotland
1752[11] 1752
Holy Roman Empire 1544 from 1583
Hungary 1582, 1587
Ireland 1752
Iceland 1700
Italy 1582
Japan 1873
Korea 1896
Latvia 1915
Lithuania 1915
Lorraine 1682, 1760
Luxembourg 1582
Moravia 1584
Netherlands, Brabant 1582
Netherlands, Drenthe 1701
Netherlands, Flanders 1583
Netherlands, Friesland 1701
Netherlands, Gelderland 1700
Netherlands, Groningen 1583, 1701
Netherlands, Holland 1583
Netherlands, Limburg 1582
Netherlands, Overijssel 1700
Netherlands, Southern Provinces 1583
Netherlands, Utrecht 1700
Netherlands, Zeeland 1582
Norway 1700
Poland 1582
Poland, Silesia 1584
Portugal 1556 1582
Prussia 1559 1610, 1700
Romania 1919
Transylvania 1590
Russia 1918
Scotland 1600[11][12] 1752
Southern Netherlands 1576[13] 1582
Spain 1556 1582
Strasbourg 1682
Sweden 1559 1753 (used modified calendar from 1700-1712)
Switzerland, Appenzell 1724
Switzerland, Basel Land 1700
Switzerland, Basel Stadt 1700
Switzerland, Bern 1700
Switzerland, Fribourg (Freiburg) 1584
Switzerland, Geneva (Genf) 1700
Switzerland, Glarus 1724
Switzerland, Grisons (Graubünden) 1812
Switzerland, Lucerne (Luzern) 1584
Switzerland, Neuchâtel 1700
Switzerland, St. Gallen (Sankt Gallen) 1724
Switzerland, Schaffhausen 1700
Switzerland, Schwyz 1584
Switzerland, Solothurn 1584
Switzerland, Thurgau 1700
Switzerland, Unterwalden (see Nidwalden and Obwalden) 1584
Switzerland, Uri 1584
Switzerland, Valais (Wallis) 1622, 1655, 1656
Switzerland, Zug 1584
Switzerland, Zürich 1700
Turkey 1927
Tuscany 1927
USSR 1918
Wales 1752
Russia 1700[14] 1918
Tuscany 1721 1750
Venice 1522 1582


Ancestor Search has published a helpful chart showing when countries and regions changed from Julian to Gregorian.

Fourmilab.ch has created a converter that converts dates from a variety of calendars, including Julian and Gregorian.

Another tool that can help with Julian and Gregorian dates, especially for Germany, is GenTools6, available as a free download from www.gentools6.de.

References

  1. Parise, Frank. The Book of Calendars. New York, New York: Facts on File, 1982. http://dpgi.unina.it/giudice/calendar/Adoption.html.
  2. GenWiki contributors, "Gregorianischer Kalender," in GenWiki, http://wiki-de.genealogy.net/Gregorianischer_Kalender, accessed 26 June 2018.
  3. Wikipedia contributors, "Gregorian calendar," in Wikipedia: the Free Encyclopedia, https://en.wikipedia.org/wiki/Gregorian_calendar#Adoption, accessed 26 June 2018.
  4. Wikipedia contributors, "Adoption of the Gregorian calendar," in Wikipedia: the Free Encyclopedia, https://en.wikipedia.org/wiki/Adoption_of_the_Gregorian_calendar, accessed 26 June 2018.
  5. "The Gregorian calendar," in The Calendar FAQ, https://www.tondering.dk/claus/cal/gregorian.php, accessed 26 June 2018.
  6. "The Change from the Julian to the Gregorian Calendar," in Ancesteor Search, http://www.searchforancestors.com/utility/gregorian.html, accessed 26 June 2018.
  7. "Countries' Calendar Reform," in Calendars through the Ages, http://www.webexhibits.org/calendars/year-countries.html, accessed 26 June 2018.
  8. Professor Robert A. Hatch, "The Gregorian Conversion," in The Scientific Revolution, http://users.clas.ufl.edu/ufhatch/pages/03-Sci-Rev/SCI-REV-Home/Historical-Research/Calendars/gregorian_calendar_history.html, accessed 26 June 2018.
  9. Herluf Nielsen: Kronologi (2nd ed., Dansk Historisk Fællesforening, Copenhagen 1967), pp.48-50.
  10. Le calendrier grégorien en France
  11. 11.0 11.1 Blackburn Holford-Strevens (1999), p. 784.
  12. John J. Bond, Handy-book of rules and tables for verifying dates with the Christian era Scottish decree on pp. xvii–xviii.
  13. Per decree of 16 June 1575. Hermann Grotefend, "Osteranfang" (Easter beginning), Zeitrechnung de Deutschen Mittelalters und der Neuzeit (Chronology of the German Middle Ages and modern times) (1891-1898)
  14. Roscoe Lamont, The reform of the Julian calendar, Popular Astronomy 28 (1920) 18–32. Decree of Peter the Great is on pp.23–24.