Theadoption 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 – theGregorian 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 universalcivil calendar, yet old style calendars remain in use in religious or traditional contexts.[1][2][a] 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 theGregorian Calendar in 1582 by thePapal bullInter gravissimas to correct an error in theJulian Calendar that was causing anerroneous calculation of the date ofEaster. The Julian Calendar had been based on ayear of 365.25days, but this was slightly too long; in reality it is circa 365.2422 days,[b] 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 excessleap days since theFirst Council of Nicaea, which establishedthe rule for dating Easter in AD 325. Consequently, he ruled, the numbering, i. e. dating, of days must jump by 10 to restore thestatus quo ante; 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 additionalleap 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 theChurch, the bull had no authority beyond ecclesial institutions and thePapal 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 becamecanon law of the Catholic Church in 1582, butProtestant churches,Eastern Orthodox Churches, and a few others did not effectuate it, and therefore the dates on which different Christian denominations celebrated Easter and otherholidays diverged.
Catholic polities such as the Catholic states of theHoly Roman Empire, theItalian principalities,Poland–Lithuania, andSpain–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,[3] which affected much of Catholic Europe, as Philip was at the time ruler ofSpain–Portugal andmuch of modern Italy.[4] In these territories,Poland–Lithuania[5] (ruled byAnna Jagiellon), and thePapal 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; theSpanish andPortuguese colonies followed somewhat laterde facto because of delay in communication of the change.[6]
Other Catholic polities soon followed.France adopted the new calendar with Sunday, 9 December 1582 being succeeded by Monday, 20 December 1582.[7]TheDutch provinces ofBrabant andZeeland, and theStates General adopted it on 25 December of that year; the provinces forming theSouthern Netherlands (modernBelgium) except theDuchy of Brabant adopted it on 1 January 1583; the province ofHolland adopted it on 12 January 1583.[8] The seven CatholicSwiss cantons adopted the new calendar in January 1584.[9]
ManyProtestant 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.[10] 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 undoubtedlythe fourth great beast of Daniel, caused the Queen to permit the matter to quietly drop.[11] In theCzech Lands, Protestants resisted the Gregorian Calendar that theHabsburg monarchy imposed. In parts of Ireland, Catholic rebels, until their defeat in theNine Years' War, retained the "new" Easter of the Gregorian Calendar in defiance of theauthorities who were loyal to England; later, Catholics practising in secret petitioned thePropaganda Fide of theHoly See fordispensation from observance of the new calendar, because it signalled disloyalty to England.[12]
The LutheranDuchy of Prussia, until 1657 still afiefdom 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.[citation needed] So 22 August was followed by 2 September 1612.[citation needed] However, this calendar change did not apply to other territories of theHohenzollern, such as Berlin-basedBrandenburg, a fief of the Holy Roman Empire.
In 1700, throughOle Rømer's influence,Denmark–Norway adopted the solar portion of the Gregorian calendar simultaneously with theBrandenburg-Pomerania and other Protestant estates of the Holy Roman Empire. Sunday, 18 February 1700, was followed by Monday, 1 March 1700.[13] None of these states adopted thelunar portion, instead calculating the date of Easter astronomically using the instant of the vernal equinox and the full moon according toKepler'sRudolphine Tables of 1627; this combination was referred to by the Protestant estates as "the improved calendar" (Der Verbesserte Kalender)[14] and considered to be distinct from the Gregorian. They finally adopted the Gregorian calculation of Easter in 1774.[15]
The remaining provinces of theDutch 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).[16]
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. KingCharles 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 introducingthe 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 laterFinland was an integral part of theSwedish kingdom at that time, hence it did the same.[17] The Russian Empire's 1809conquest ofFinland 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.
Through enactment of theCalendar (New Style) Act 1750,Great Britain andits 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 acomputation for the date of Easter that achieved the same result as Gregory's rules, without actually referring to him.[18]
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 ofdual 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.
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 twoSwiss communes ofSchiers andGrüsch were the last areas of Western and Central Europe to switch to the Gregorian calendar, in 1812.[9]
Many of the countries ofeastern Europe wereEastern Orthodox orIslamic and adopted the Gregorian calendar much later thanwestern Christian countries. Catholic countries such as thePolish–Lithuanian Commonwealth adopted the "new style" (N.S.) Gregorian calendar in 1582 (switched back in 1795 after theThird Partition of Poland), but the switch to the Gregorian calendar for secular use occurred inEastern Orthodox countries as late as the 20th century. Some religious groups in some of these countries, known asOld Calendarists, still use the "old style" (O.S.) Julian calendar for ecclesiastical purposes.
TheKingdom of Bulgaria changed from the Julian to the Gregorian calendar in 1916 during theFirst World War. 31 March was followed by 14 April 1916.[19]
TheOttoman Empire'sRumi calendar, used for fiscal purposes, was realigned from a Julian to a Gregorian starting on 16 February / 1 March 1917. The beginning of the year was reset to 1 January starting in 1918.[c] The numbering of the years, though, remained uniquely Turkish untilTurkey adopted the Gregorian calendar on 1 January 1926.[20]
InRussia, the Gregorian calendar was accepted after theOctober Revolution. On 24 January 1918, theCouncil of People's Commissars issued adecree that Wednesday, 31 January 1918, was to be followed by Thursday, 14 February 1918, thus dropping 13 days from the calendar.[d] The decree required that the Julian date was to be written in parentheses after the Gregorian date, until1 July 1918.[21] With the change, the October Revolution itself, once converted, took place on 7 November. Articles about the October Revolution that mention this date difference tend to do a full conversion to the dates from Julian to the Gregorian calendar. For example, in the article "The October (November) Revolution" theEncyclopædia Britannica uses the format of "25 October (7 November, New Style)" to describe the date of the start of the revolution.[22]
In the territory of modernUkraine, the Gregorian calendar was officially adopted for secular use immediately after its adoption by Pope Gregory XIII in 1582, as most of Ukraine then was part of the predominantly CatholicPolish-Lithuanian Commonwealth. TheRoman Catholic Church in Ukraine switched to the new calendar at the same time. However, the Orthodox churches in the Commonwealth refused to accept a calendar instigated by a Roman Catholic Pope, so theOrthodox Church of Ukraine continued following the old Julian calendar until 2023.
In 2018, theUkrainian Lutheran Church switched to theRevised Julian calendar. After the Russian invasion in 2022, most other Christian denominations that were still using the old Julian calendar announced that they would transition to the Gregorian or the Revised Julian calendar. TheAll-Ukrainian Union of Churches of Evangelical Christian Baptists and the Church of Christians of the Evangelical Faith of Ukraine (Pentecostals) switched to the Gregorian calendar the same year. On 1 September 2023, theUkrainian Greek Catholic Church switched to the Gregorian calendar, while the Orthodox Church of Ukraine opted for the Revised Julian calendar. At the same time, theUkrainian Orthodox Church (Moscow Patriarchate) declared that it would continue to celebrate the birth of Christ according to the Julian calendar.
Other countries of Eastern Europe, most notablyEastern Orthodox countries, adopted the Gregorian calendar for secular purposes in the 1910s or early 1920s. By the 20th century, the date on the Julian calendar was 13 days behind that on the Gregorian calendar.Romania adopted the Gregorian in 1919, with 31 March 1919 being followed by 14 April 1919.
The last country of Eastern Orthodox Europe to adopt the Gregorian calendar for secular purposes was Greece, at the time under military administration following the11 September 1922 Revolution. The date of change was 1 March 1923. As a consequence, Wednesday 15 February 1923 in the Greek calendar was followed by Thursday 1 March 1923.[13][23] The decree expressly limited the reform to lay (i.e. non-religious) matters, so the reform did not affect the dates of religious holidays. (See below.)
While the civil administrations of Eastern European countries adopted the Gregorian calendar in the 1910s or early 1920s, none of the nationalEastern Orthodox Churches have recognised the Gregorian calendar for church or religious purposes. Instead, theRevised Julian calendar was proposed in May 1923 at theCouncil of Constantinople. It uses a different leap year rule, leading to the mean year being slightly shorter than that of the Gregorian calendar, while being constructed in such a way as to maximise the time before its dates start to diverge from the Gregorian. There will be no difference between the two calendars until 2800.
TheGreek Orthodox Church of Jerusalem,Russian Orthodox Church,Serbian Orthodox Church,Georgian Orthodox and Apostolic Church,Polish Orthodox Church,Macedonian Orthodox Church and theGreek Old Calendarists did not accept the Revised Julian calendar, and continue to celebrate Christmas on 25 December in the Julian calendar, which is 7 January in the Gregorian calendar until 2100.
All of the other Eastern churches, theOriental Orthodox churches (Coptic Orthodox Church of Alexandria,Ethiopian Orthodox Tewahedo Church,Eritrean Orthodox Tewahdo Church, andSyriac Orthodox Church) continue to use their own calendars, which usually result in fixed dates being celebrated in accordance with the Julian calendar. This is most interesting in the case of the Syriac Orthodox Church, as one of its Patriarchs,Ignatius Nemet Allah I, was one of the nine scholars who devised the Gregorian calendar.[24] TheIndian Orthodox Church uses the Gregorian calendar along with their autonomous Syriac Orthodox counterparts in India, theMalankara Jacobite Syriac Orthodox Church.
TheArmenian Apostolic Church adopted the Gregorian calendar in 1923, except in theArmenian Patriarchate of Jerusalem, where the old Julian calendar is still in use.[25][26]
The European colonies ofthe Americas adopted the change when their mother countries did. In North America,New France andNew Spain had adopted the new calendar in 1582. The British colonies of Canada and theThirteen Colonies followed suit in 1752, as declared by the Britishcalendar act. In the rest of South America, the Portuguese colonies also changed in 1582. Practice in the Caribbean followed that of their British, Dutch, French and Spanish colonists
Alaska remained on the Julian calendar along with the rest of Russia until 1867, when the territory wassold to the United States. At noon on Saturday, 7 October 1867 (Julian), the date changed to Friday, 18 October 1867 (Gregorian). Although the Julian calendar was 12 days behind the Gregorian calendar, only 11 days were skipped because Alaska also moved from the Eurasian side of theInternational Date Line to the American side.[27]
Japan,Korea, and China started using the Gregorian calendar on1 January 1873,1 January 1896, and1 January 1912, respectively.[28][29]They previously usedlunisolar calendars. The Old Style and New Style dates in these countries usually mean the older lunisolar dates and the newer Gregorian calendar dates respectively. In these countries, the old style calendars were similar but not all the same. TheArabic numerals may be used for both calendar dates in modern Japanese and Korean languages, but not for Chinese old-style dates.
Japan decided to officially replaceits traditional lunisolar calendar with the Gregorian calendar in 1872, so the day following31 December 1872 as "the second day of the twelfth month of Meiji 5" (明治5年12月2日,Meiji gonen jūnigatsu futsuka) became1 January 1873,[28] locally known as "the first day of the first month of Meiji 6" (明治6年1月1日,Meiji rokunen ichigatsu tsuitachi). (The Japanese rendering of the Western months is simplyichi-gatsu or "One-month" for January,ni-gatsu or "Two-month" for February, etc.[30]) This brought Japan's calendar in alignment with that of the major Western powers (excluding Russia).
To this day, however, it is common to usereign names (nengō), especially for official documents; for instance,Meiji 1 for 1868,Taishō 1 for 1912,Shōwa 1 for 1926,Heisei 1 for 1989,Reiwa 1 for 2019, and so on. The months and days are those of the Gregorian calendar, but the year is either the "Western calendar" (西暦,seireki) year number per theCommon Era orAnno Domini system, or a year of the nengō of the emperor on the throne. Since 1873, an era and the first year of that era has begun on the day of the year that the emperor ascended the throne. The second year of that era began on the next 1 January even if the first year contained only a few days. All subsequent years of that era began on 1 January until that emperor died or abdicated. For example, the first year of theShowa Era, that of EmperorHirohito, contained only the last six days of 1926, while Showa 64, his last year, contained only the first seven days of 1989. The current Gregorian year 2026 corresponds toReiwa 8.
Replacing its years numbered from 1392, the founding of theJoseon dynasty,[31][32]Korea started using the Gregorian calendar on 1 January 1896, which was the 17th day of the 11th lunar month not only in Korea but also inChina, which still used the lunisolar calendar.[29] YetKorean era names were used for its years through 1910; and between 1910 and 1945, whenKorea was under Japanese rule,Japanese era names were used to count the years of the Gregorian calendar used in Korea.
InSouth Korea, from 1945 until 1961, Gregorian calendar years were also counted from the foundation ofGojoseon in 2333BC (regarded as year one), the date of the legendary founding of Korea byDangun, hence these Dangi (단기) years were 4278 to 4294. This numbering was informally used with theKorean lunar calendar before 1945 but is only occasionally used today. Since 1997,North Korea officially counts years based on theJuche era, the first year of which is 1912, the year ofKim Il Sung's birth, with Gregorian months and days. The current Gregorian year 2026 corresponds to Juche year 115.
At its founding on1 January 1912, theRepublic of China (ROC) government under Provisional PresidentSun Yat-sen abolished the lunisolarChinese calendar and adopted the Gregorian calendar. The public, however, resisted the change and continued to observe traditional holidays. PresidentYuan Shikai switched to a dual-calendar policy, under which the Gregorian calendar was to be used for most purposes except traditional holidays, which were to be timed according to the Chinese calendar; this would also be followed by the short-livedEmpire of China.[e] With the1928 unification of China under theKuomintang, theNationalist government decreed that, effective1 January 1929, the Gregorian calendar would be used. TheRepublic of China calendar would retain the Chinese traditions of numbering the months with a modified era system, determined according to the traditionalChinese era names, but using the founding of the Republic of China government in 1912 as the start (epoch) rather than theregnal year of an emperor. The current Gregorian year 2026 corresponds to the ROC year 115. This system is still in use inTaiwan where the ROC government retains controlsince 1945.
Upon its foundation in 1949, thePeople's Republic of China continued to use the Gregorian calendar with numbered months and adopted Western numbered years, but timed traditional holidays according to the Chinese calendar and abolished the ROC Era System. Today mainland China (including Hong Kong and Macau), Taiwan, Malaysia, Indonesia and Singapore all observe traditional holidays based on the traditional calendar, such asChinese New Year, while timing other holidays, especially national anniversaries, according to the Gregorian calendar. The adopted calendar in both mainland China and Taiwan is called thePublic Calendar (simplified Chinese:公历;traditional Chinese:公曆;pinyin:Gōnglì), or "New Calendar" (simplified Chinese:新历;traditional Chinese:新曆;pinyin:Xīnlì).
TheChinese language may distinguish old and new style dates in different ways:
| Grammar | Chinese calendar | Gregorian calendar |
|---|---|---|
| Writing a date in Chinese characters | Yes as the rule[33][34] | Yes as an option[35] |
| Writing a date in Arabic numerals | No[f][g] | Yes as an option[35] |
| Omitting 日 (rì, day) from a date | Yes as an option[33] | No, unless also omitting 月 (yuè, month), e.g.一·二八 (yī èrbā, January 28, 1931) and一二·九 (yīèr jiǔ, December 9, 1935) by pausing between a month and a day to disambiguate[36] |
| Prefixing 初 (chū, initial) for the first 10 days of a month[37] | Yes as an option[33][38] | No[h] |
| 正月 (zhēngyuè) as the first month[39] | Yes[40] | No |
| 元月 (yuányuè) or 一月 (yīyuè) as the first month[41] | Yes as an option | Yes |
| 冬月 (dōngyuè) as the eleventh month[42] | Yes as an option | No, write November as 11月 or 十一月 (shíyīyuè, month 11) |
| 臘月 (làyuè) as the twelfth month[43] | Yes as an option | No, write December as 12月 or 十二月 (shíèryuè, month 12) |
In speaking, people generally call the date in the Gregorian calendar month "No.dd" (simplified Chinese:dd号;traditional Chinese:dd號); for example, theSpring Festival of year 2017 is No. 28 of Month 1 (simplified Chinese:1月28号;traditional Chinese:1月28號). On the other hand, people never call dates on the Chinese calendar as "No.dd"., which avoids any possible ambiguity.
When referencing dates before the introduction of the Gregorian calendar in 1582, the official Chinese calendar may either inherit the issues with earlier calendars to be historically correct[i] or follow theproleptic Gregorian calendar if so specified.[j]
Vietnam adopted the Gregorian calendar in 1954, replacing theVietnamese calendar, which was based on the Chinese calendar. Like China, Vietnam still uses the Vietnamese calendar to observe lunisolar holidays and celebrations.[44]
The Gregorian calendar replaced theBurmese calendar in several mainland Southeast Asian kingdoms in the second half of the 19th century. This took place in Cambodia in 1863 and Laos in 1889.[45] Since the British conquest of theKonbaung dynasty in 1886, the Gregorian calendar has been used alongside the Burmese calendar inMyanmar.
In 1889,Siam also switched to the Gregorian calendar as the official civil calendar, with theRattanakosin Era (with 1782 as Year 1).[46] TheThai lunar calendar remains in use for religious purposes.
TheIslamic calendar is a lunar one so there are twelvelunar months in a year of 354 or 355 days, being 11 days shorter than asolar year. Consequently, holy days in Islam migrate around the solar year on a 32-year cycle.[47] Some countries in the Islamic world use the Gregorian calendar for civil purposes, while retaining the Islamic calendar for religious purposes. For example,Saudi Arabia adopted the Gregorian calendar for the purpose of paying public sector staff effective 1 October 2016; private sector employers had already adopted the Gregorian calendar for pay purposes.[47][48]
 | This sectionneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources in this section. Unsourced material may be challenged and removed.(December 2016) (Learn how and when to remove this message) |
Today, the vast majority of countries use the Gregorian calendar as their sole civil calendar. The four countries which have not adopted the Gregorian calendar are Ethiopia (Ethiopian calendar),[49] Nepal (Vikram Samvat andNepal Sambat), Iran and Afghanistan (Solar Hijri calendar).[50]
Some countries use other calendars alongside the Gregorian calendar, including India (Indian national calendar), Bangladesh (Bengali calendar), Pakistan (Islamic calendar), Israel (Hebrew calendar) and Myanmar (Burmese calendar), and other countries use a modified version of the Gregorian calendar, including Thailand (Thai solar calendar), Japan (Japanese calendar), North Korea (North Korean calendar) and Taiwan (Minguo calendar).
While many religious organizations reckon theirliturgical year by the Gregorian civil calendar, others have retained their own calendars.Alternative calendars are used in many regions of the world today to mark cycles of religious and astrological events.
The use of different calendars had the potential to cause confusion between contemporaries. For example, it is related[51] that one of the contributory factors forNapoleon's victory at theBattle of Austerlitz was the confusion between the Russians, who were using the Julian calendar, and the Austrians, who were using the Gregorian calendar, over the date that their forces should combine.[52] However, this tale is not supported in a contemporary account from a major-general of the Austrian Imperial and Royal Army,Karl Wilhelm von Stutterheim, who tells of a joint advance of the Russian and Austrian forces (in which he himself took part) five days before the battle,[53] and it is explicitly rejected in Goetz's 2005 book-length study of the battle.[54]
The date when each country adopted the Gregorian calendar, or an equivalent, is marked against a horizontal timeline. The vertical axis is used for expansion to show separate national names for ease in charting, but otherwise has no significance.
{{cite book}}:ISBN / Date incompatibility (help)battle of austerlitz.