The adoption of the Gregorian Calendar has taken place in the history of most cultures and societies around the world, marking a change from one of various traditional (or "old style") dating systems to the contemporary (or "new style") system the Gregorian Calendar which is widely used around the world today. Some polities adopted the new calendar in 1582, others not before the early twentieth century, and others at various dates between. A few have yet to do so, but except for these, the Gregorian Calendar is now the universal civil calendar, yet old style calendars remain in use in religious or traditional contexts.Introduction to Calendars . United States Naval Observatory. Retrieved 15 January 2009.Calendars by L. E. Doggett. Section 2. During and for some time after the transition between systems, it has been common to use the terms "Old Style" and "New Style" in dating to indicate which calendar was used to reckon them.
Pope Gregory XIII instituted the Gregorian Calendar in 1582 by the Papal bull to correct an error in the Julian Calendar that was causing an erroneous calculation of the date of Easter. The Julian Calendar had been based on a year of 365.25 days, but this was slightly too long; in reality it is circa 365.2422 days, and so over centuries the Calendar had drifted increasingly out of alignment with the orbit of Earth. According to Gregory's scientific advisors, the Calendar had acquired 10 excess leap days since the First Council of Nicaea, which established the rule for dating Easter in AD 325. Consequently, he ruled, the numbering, i. e. dating, of days must jump by 10 to restore the ; thus, for example, when the Catholic polities of Europe adopted the Gregorian Calendar, the day after Thursday, 4 October 1582 was dated as Friday, 15 October 1582. Polities that did not change calendars until the 18th century had by then observed 1700 as an additional leap year, necessitating the omission of 11 dates from the reckoning. Some polities did not change until the 19th or 20th centuries, necessitating the omission of 12 or 13 dates.
Although Gregory's reform was instituted in the most solemn of forms available to the Church, the bull had no authority beyond ecclesial institutions and the Papal States. The changes he proposed were to the civil calendar, which was not directly subject to Papal authority. For these changes to be legally effectuated, the civil authority of each polity was needed. The bull became canon law of the Catholic Church in 1582, but Protestant churches, Eastern Orthodox Churches, and a few others did not effectuate it, and therefore the dates on which different Christian denominations celebrated Easter and other holidays diverged.
Adoption in Catholic polities Catholic polities such as the Catholic states of the Holy Roman Empire, the Italian principalities, Poland–Lithuania, and Spain–Portugal and its European and overseas possessions were first to adopt the Gregorian Calendar: Thursday, 4 October 1582 was succeeded by Friday, 15 October 1582, with 10 dates between omitted.
Philip II of Spain decreed the change from the Julian to Gregorian Calendar, which affected much of Catholic Europe, as Philip was at the time ruler of Spain–Portugal and much of modern Italy. In these territories, Poland–Lithuania (ruled by Anna Jagiellon), and the Papal States, the Gregorian Calendar was implemented on the date that the bull prescribed, with Julian Thursday, 4 October 1582 being succeeded by Gregorian Friday, 15 October 1582; the Spanish and Portuguese colonies followed somewhat later de facto because of delay in communication of the change."Pragmatica" on the Ten Days of the Year World Digital Library, the first known South American imprint, produced in 1584 by Antonio Ricardo, of a four-page edict issued by King Philip II of Spain in 1582, decreeing the change from the Julian to the Gregorian Calendar.
Other Catholic polities soon followed. France adopted the new calendar with Sunday, 9 December 1582 being succeeded by Monday, 20 December 1582.Delatour, Jérôme, "Noël le 15 décembre: La réception du calendrier grégorien en France (1582)", Bibliothèque de l'école des chartes, 157 (1999), 369-416 Persee link. The Dutch provinces of Brabant and Zeeland, and the States General adopted it on 25 December of that year; the provinces forming the Southern Netherlands (modern Belgium) except the Duchy of Brabant adopted it on 1 January 1583; the province of Holland adopted it on 12 January 1583. The seven Catholic Swiss cantons adopted the new calendar in January 1584.
Adoption in Protestant polities Many Protestant polities initially objected to adoption of a Catholic innovation; some Protestants feared the new calendar was part of a plot to return them to the Catholic fold. In England, for example, Queen Elizabeth I and her privy council had looked favourably to a Gregorian-like royal commission recommendation to omit 10 dates from the Julian Calendar, but the virulent opposition of the Anglican bishops, who argued that the Pope was undoubtedly the fourth great beast of Daniel, caused the Queen to permit the matter to quietly drop. In the Czech Lands, Protestants resisted the Gregorian Calendar that the Habsburg monarchy imposed. In parts of Ireland, Catholic rebels, until their defeat in the Nine Years' War, retained the "new" Easter of the Gregorian Calendar in defiance of the authorities who were loyal to England; later, Catholics practising in secret petitioned the Propaganda Fide of the Holy See for dispensation from observance of the new calendar, because it signalled disloyalty to England.
Denmark-Norway and Brandenburg-Pomerania In 1700, through Ole Rømer's influence, Denmark–Norway adopted the solar portion of the Gregorian calendar simultaneously with the Brandenburg-Pomerania and other Protestant estates of the Holy Roman Empire. Sunday, 18 February 1700, was followed by Monday, 1 March 1700.Nørby, Toke. The Perpetual Calendar None of these states adopted the lunar portion, instead calculating the date of Easter astronomically using the instant of the vernal equinox and the full moon according to Kepler's Rudolphine Tables of 1627; this combination was referred to by the Protestant estates as "the improved calendar" (Der Verbesserte Kalender) and considered to be distinct from the Gregorian. They finally adopted the Gregorian calculation of Easter in 1774.
Rest of the Dutch Republic The remaining provinces of the Dutch Republic adopted the Gregorian calendar on 12 July 1700 (Gelderland), 12 December 1700 (Overijssel and Utrecht), 12 January 1701 (Friesland and Groningen) and 12 May 1701 (Drenthe).
Great Britain and its colonies
Through enactment of the Calendar (New Style) Act 1750, Great Britain and its possessions (including parts of what is now the United States) adopted the Gregorian calendar in 1752, by which time it was necessary to correct by 11 days. Wednesday, 2 September 1752, was followed by Thursday, 14 September 1752. In Great Britain, the term "New Style" was used for the calendar and the Act omits any acknowledgement of Pope Gregory: the Annexe to the Act established a computation for the date of Easter that achieved the same result as Gregory's rules, without actually referring to him.
With the same Act, the Empire (except Scotland, which had already done so from 1600) changed the start of the civil year from 25 March to 1 January. Consequently, the custom of dual dating (giving a date in both old and new styles) can refer to the Julian/Gregorian calendar change, or to the start of year change, or to both.
Prussia The Lutheran Duchy of Prussia, until 1657 still a fiefdom of Catholic Poland, was the first Protestant state to adopt the Gregorian calendar. Under the influence of its liege lord, the King of Poland, it agreed in 1611 to do so. So 22 August was followed by 2 September 1612. However, this calendar change did not apply to other territories of the Hohenzollern, such as Berlin-based Brandenburg, a fief of the Holy Roman Empire.
Sweden
Sweden's transition to the Gregorian calendar was difficult and protracted. Sweden started to make the change from the Julian calendar and towards the Gregorian calendar in 1700, but it was decided to make the (then 11-day) adjustment gradually by excluding the leap days (29 February) from each of 11 successive leap years, 1700 to 1740. Meanwhile, the Swedish calendar would be out of step with both the Julian calendar and the Gregorian calendar for 40 years; also, the difference would not be constant but would change every four years. This system had the potential for confusion when working out the dates of Swedish events in this 40-year period. To add to the confusion, the system was poorly administered, and the leap days that should have been excluded in 1704 and 1708 were not excluded. The Swedish calendar (according to the transition plan) should have been 8 days behind the Gregorian but was 10 days behind. King Charles XII recognised that the gradual change to the new system was not working, and he abandoned it.
Rather than proceeding directly to the Gregorian calendar, it was decided to revert to the Julian calendar. This was achieved by introducing the unique date 30 February in 1712, adjusting the discrepancy in the calendars from 10 back to 11 days. Sweden finally adopted the solar portion of the Gregorian calendar in 1753, when Wednesday, 17 February, was followed by Thursday, 1 March. What became later Finland was an integral part of the Swedish kingdom at that time, hence it did the same.Mike Spathaky, "Old Style and New Style Dates and the change to the Gregorian Calendar: A summary for genealogists" The Russian Empire's 1809 conquest of Finland did not revert this, since autonomy was granted, but government documents in Finland were dated in both the Julian and Gregorian styles. This practice ended when independence was gained in 1917.
Rest of Switzerland As noted above, the Catholic cantons of Switzerland adopted the new calendar in 1582. Geneva and several Protestant cantons adopted it in January 1701 or at other dates throughout the 18th century. The two Swiss communes of Schiers and Grüsch were the last areas of Western and Central Europe to switch to the Gregorian calendar, in 1812.
Adoption in Eastern Europe Many of the countries of eastern Europe were Eastern Orthodox or Islamic and adopted the Gregorian calendar much later than western Christian countries. Catholic countries such as the Polish–Lithuanian Commonwealth adopted the "new style" (N.S.) Gregorian calendar in 1582 (switched back in 1795 after the Third Partition of Poland), but the switch to the Gregorian calendar for secular use occurred in Eastern Orthodox countries as late as the 20th century. Some religious groups in some of these countries, known as Old Calendarists, still use the "old style" (O.S.) Julian calendar for ecclesiastical purposes.
The Kingdom of Bulgaria changed from the Julian to the Gregorian calendar in 1916 during the First World War. 31 March was followed by 14 April 1916.See .
Turkey
The Ottoman Empire's Rumi calendar, used for fiscal purposes, was realigned from a Julian to a Gregorian basis starting on 16 February / 1 March 1917. The beginning of the year was reset to 1 January starting in 1918. The numbering of the years, though, remained uniquely Turkish until Turkey adopted the Gregorian calendar on 1 January 1926. The transition left a visible trace in historical records: gravestones from the early Republican era in cemeteries such as Feriköy Cemetery commonly show birth years in the Hijri calendar and death dates in the Gregorian calendar. Since exact birth dates were often unrecorded and a Hijri year usually spans two Gregorian years, the precise Gregorian birth year cannot be determined from these inscriptions.
Russia