Julian and Gregorian Calendars

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The official calendar used in most of the modern world today is the Gregorian, named after Pope Gregory. It is based on the earth’s movement in relation to the sun with common and leap years comprising 365 and 366 days respectively.

When the old Julian calendar (which added 11 minutes every year) was replaced by the more accurate Gregorian calendar in 1582, only a few countries accepted the change. It took almost 400 years before all of Europe adopted the new standard.

Dates recorded from 1582 to 1919 that crossed the two systems can be confusing to family history researchers. For 46 years Benjamin Franklin’s birth day was January 6, 1706. He was “reborn” to January 17th when the British Colonies adopted the Gregorian Calendar in 1752.

A chart which shows when countries changed from Julian to Gregorian and a converter that translates dates from a variety of calendars are among the tools available to navigate through this maze. Interesting historical reading about how a monarch's reign influenced the English calendar is found in the article Regnal Years in England.

Country Start numbered year
on 1 January
Adoption of
Gregorian Calendar
Denmark Gradual change from
13th to 16th centuries[1]
Venice 1522 1582
Holy Roman Empire 1544 from 1583
Spain 1556 1582
Portugal 1556 1582
Prussia 1559 1700
Sweden 1559 1753
France 1564[2] 1582
Southern Netherlands 1576[3] 1582
Lorraine 1579 1682
Dutch Republic 1583 from 1582
Scotland 1600[4][5] 1752
Russia 1700[6] 1918
Tuscany 1721 1750
Britain and
British Empire
except Scotland
1752[4] 1752


  1. Herluf Nielsen: Kronologi (2nd ed., Dansk Historisk Fællesforening, Copenhagen 1967), pp.48-50.
  2. Le calendrier grégorien en France
  3. 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)
  4. 4.0 4.1 Blackburn & Holford-Strevens (1999), p. 784.
  5. John J. Bond, Handy-book of rules and tables for verifying dates with the Christian era Scottish decree on pp. xvii–xviii.
  6. Roscoe Lamont, The reform of the Julian calendar, Popular Astronomy 28 (1920) 18–32. Decree of Peter the Great is on pp.23–24.