Adoption of the Gregorian calendar

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.

According to Gregory's scientific advisers, the calendar had acquired ten excess leap days since the First Council of Nicaea (which established the rule for dating Easter in AD 325).

Countries which did not change until the 18th century had by then observed an additional leap year (1700), necessitating the removal of eleven days from the reckoning.

Although Gregory's reform was enacted in the most solemn of forms available to the Church, the bull had no authority beyond ecclesial institutions and the Papal States.

In these territories, as well as in the Polish–Lithuanian Commonwealth (ruled by Anna Jagiellon) and in the Papal States, the new calendar was implemented on the date specified by the bull, with Julian Thursday, 4 October 1582, being followed by Gregorian Friday, 15 October 1582; the Spanish and Portuguese colonies followed somewhat later de facto because of delay in communication.

[8] In England for example, Queen Elizabeth I and her privy council had looked favourably to a Gregorian-like royal commission recommendation to drop 10 days from the calendar but the virulent opposition of the Anglican bishops, who argued that the Pope was undoubtedly the fourth great beast of Daniel, led the Queen to let the matter be quietly dropped.

[10] The Lutheran Duchy of Prussia, until 1657 still a fiefdom of Catholic Poland, was the first Protestant state to adopt the Gregorian calendar.

[citation needed] 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.

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.

[11] 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" (Verbesserte Kalender) and considered to be distinct from the Gregorian.

[12] 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).

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.

The Gregorian calendar was applied in the British colonies in Canada and the future United States east of the Appalachian Mountains in 1752.

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.

[17] The Ottoman Empire's Rumi calendar, used for fiscal purposes, was realigned from a Julian to a Gregorian starting on 16 February / 1 March 1917.

[c] The numbering of the years, though, remained uniquely Turkish until Turkey adopted the Gregorian calendar on 1 January 1926.

At the same time, the Ukrainian Orthodox Church (Moscow Patriarchate) declared that it would continue to celebrate the birth of Christ according to the Julian calendar.

The last country of Eastern Orthodox Europe to adopt the Gregorian calendar for secular purposes was Greece, at the time under military administration following the 11 September 1922 Revolution.

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.

(The Japanese rendering of the Western months is simply ichi-gatsu or "One-month" for January, ni-gatsu or "Two-month" for February, etc.

To this day, however, it is common to use reign 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.

[e] With the 1928 unification of China under the Kuomintang, the Nationalist government decreed that, effective 1 January 1929, the Gregorian calendar would be used.

The Republic of China calendar would retain the Chinese traditions of numbering the months with a modified era system, determined according to the traditional Chinese era names, but using the founding of the Republic of China government in 1912 as the start (epoch) rather than the regnal year of an emperor.

Upon its foundation in 1949, the People'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 as Chinese New Year, while timing other holidays, especially national anniversaries, according to the Gregorian calendar.

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.

Alternative calendars are used in many regions of the world today to mark cycles of religious and astrological events.

[48] 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,[49] and it is explicitly rejected in Goetz's 2005 book-length study of the battle.

The vertical axis is used for expansion to show separate national names for ease in charting, but otherwise has no significance.