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'Old Style' (or 'OS') and 'New Style' (or 'NS') is used in English language historical studies either to indicate that the start of the Julian year has been adjusted to start on 1 January (NS) even though contemporary documents use a different start of year (OS); or to indicate that a date conforms to the Julian calendar (OS), formerly in use in many countries, rather than the Gregorian calendar (NS).Death warrant of Charles I web page of the UK National Archives.A demonstration of New Style meaning Julian calendar with a start of year adjustment.The October (November) Revolution Britannica encyclopaedia, A demonstration of New Style meaning the Gregorian calendar.Stockton, J.R. Date Miscellany I: The Old and New Styles "The terms 'Old Style' and 'New Style' are now commonly used for both the 'Start of Year' and 'Leap Year' [(Gregorian calendar)] changes (England & Wales: both in 1752; Scotland: 1600, 1752). I believe that, properly and historically, the 'Styles' really refer only to the 'Start of Year' change (from March 25th to January 1st); and that the 'Leap Year' change should be described as the change from Julian to Gregorian."Spathaky, Mike Old Style New Style dates and the change to the Gregorian calendar. "increasingly parish registers, in addition to a new year heading after 24th March showing, for example '1733', had another heading at the end of the following December indicating '1733/4'. This showed where the New Style 1734 started even though the Old Style 1733 continued until 24th March. ... We as historians have no excuse for creating ambiguity and must keep to the notation described above in one of its forms. It is no good writing simply 20th January 1745, for a reader is left wondering whether we have used the Old or the New Style reckoning. The date should either be written 20th January 1745 OS (if indeed it was Old Style) or as 20th January 1745/6. The hyphen (1745-6) is best avoided as it can be interpreted as indicating a period of time."
Many other cultures have also changed their calendar system to adopt Common Era dating and thus have old and new styles of dating: these are discussed briefly later in the article.

Contents

Differences between the start of the year

Differences between Julian and Gregorian dates

Possible date conflicts

Countries that used lunisolar calendars

Japan

Korea

China

See also

Further reading

Footnotes

Differences between the start of the year

When recording British history it is usual to use the dates recorded at the time of the event with the year adjusted to the start on the 1 January. So for example the Battle of Hastings is universally known to have been fought on 14 October, 1066. But the start of the Julian year was not always 1 January and was altered at different times in different countries.
From the 12^th century to 1752 the year in England began on 25 March (Lady Day),^[2] so for example the execution of Charles I was recorded at the time in Parliament as happening on 30 January 164'8' (Old Style). House of Commons Journal Volume 8, 9 June 1660 (Regicides) In modern English language texts this date is usually recorded as "30 January 164'9'" (New Style). A full conversion of the date into the Gregorian calendar is 9 February 1649, the date by which his contemporaries in some parts of continental Europe would have recorded his execution.
The OS/NS designation is particularly relevant for dates which fall between the start of the modern year (1 January) and the start of the contemporary year, which was 25 March in England up and until 1752 (see Julian year article).
During the transition years between the first introduction of the Gregorian calendar on continental Europe and its introduction in Britain, contemporary usage in England started to change. In Britain 1 January was celebrated as the New Year festival,^[3] but the "year starting 25th March was called the Civil or Legal Year, although the phrase Old Style was more commonly used." To reduce misunderstandings on the date, it was not uncommon in parish registers for a new year heading after 24 March for example 1661 had another heading at the end of the following December indicating "1661/62". This was to explain to the reader that the year was 1661 Old Style and 1662 New Style.Spathaky, Mike Old Style New Style dates and the change to the Gregorian calendar. "An oblique stroke is by far the most usual indicator, but sometimes the alternative final figures of the year are written above and below a horizontal line, as in a fraction (a form which cannot easily be reproduced here in ASCII text). Very occasionally a hyphen is used, as 1733-34."

Differences between Julian and Gregorian dates

'Conversion of Julian to Gregorian dates'

Time period (from March 1 of first year to February 29 of last year)	Сorrection, days
1–100	-2
100–200	-1
200–300	0
300–500	+1
500–600	+2
600–700	+3
700–900	+4
900–1000	+5
1000–1100	+6
1100–1300	+7
1300–1400	+8
1400–1500	+9
1500–1700	+10
1700–1800	+11
1800–1900	+12
1900–2100	+13
2100–2200	+14

The Julian calendar was formerly in use in many European countries and their colonies, rather than the Gregorian calendar, currently in use in most countries. Consequently and to avoid ambiguity, "Old Style" (OS) and "New Style" (NS) are sometimes added to historical dates to identify which system is being used (when giving a date in the period when both systems were in parallel use). This notation is used in Western European (and colonial) history: similar notations are in use for the equivalent conversions in Eastern Europe and Asia.
For a period of 170 years (1582 – 1752), both dating systems were in concurrent use in different parts of Western Europe and its colonies. The Julian calendar had drifted by 11 days from the solar calendar (due to its surfeit of leap years), so the day and month differ between the systems as well as does the year. System conversion occurred in Eastern Orthodox countries as late as the twentieth century.
Catholic countries such as Italy, Poland, Spain, and Portugal were first to change to the Gregorian calendar. Thursday, 4 October 1582 was followed by Friday, 15 October 1582, with ten days "missing". Countries that did not change until the 1700s observed an additional leap year, necessitating eleven "missing days". Some countries did not change until the 1800s or 1900s, necessitating one or two more "missing days".
France changed from Julian to Gregorian Calendar on 9 December 1582 JU where the next day was 20 December 1582 GR. France used the French Republican Calendar from 22 September 1792 GR to 31 December 1805 GR.
In Russia, the terms "Old Style" and "New Style" have the same significance as elsewhere. The start of the year was moved to January 1 in 1700, but the Gregorian calendar was introduced there much later, in the Russian SFSR — on February 14 1918 (Gregorian calendar). Hence the October Revolution of 1917 is so called, despite having started on November 7 under the Gregorian calendar (October 25 [Julian calendar]). Articles about the October Revolution which mention this date difference tend to do a full conversion to the dates from Julian to the Gregorian calendar. For example the article "The October (November) Revolution" the ''Encyclopædia Britannica'' uses the format of "25 October (7 November, New Style);" to describe the date of the start of the revolution.^[4]
It is sometimes remarked that William Shakespeare and Miguel de Cervantes died on the same ''date'', 23 April 1616, but not on the same ''day''. England was still using the Julian calendar in 1616, while Spain was using the Gregorian calendar. Cervantes actually died ten days before Shakespeare.

Possible date conflicts

Occasionally using different calendars has caused confusion between contemporaries. For example one of the contributory factors for Napoleon's victory at the Battle 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.^[5]
Usually, the mapping of new dates onto old dates with a start of year adjustment works well with little confusion for events which happened before the introduction of the Gregorian Calendar. For example the Battle of Agincourt is universally known to have been fought on 25 October 1415, which is Saint Crispin's Day. But for the period between the first introduction of the Gregorian calendar on 15 October 1582 and its introduction in Britain on 14 September 1752, there can be considerable confusion between events in continental western Europe and in British domains. Events in continental western Europe are usually reported in English language histories as happening under the Gregorian calendar. For example the Battle of Blenheim is always given as 13 August 1704. However confusion occurs when an event affects both. For example William III of England arrived at Brixham in England on 5 November (Julian calendar), after setting sail from the Netherlands on 11 November (Gregorian calendar). To add to the confusion, the Battle of Boyne, which took place only a few months later in Ireland on 1 July "Old Style", is not mapped to 1 July "New Style" but is remembered as taking place on 12 July. The keeping of the recorded date (not a mapped date) for the anniversary of this battle has more to do with Protestants not at first recognising Gregorian dates, so they continued to celebrate the anniversary on their Protestant 1 July and now traditionally do so.
Because of the differences, English people and their correspondents often employed two dates, more or less automatically, as Benjamin Woolley observed in his biography of Dr John Dee, ''The Queen's Conjurer''. Dee fought unsuccessfully for England to embrace the 1583/4 date set for the change. Woolley wrote because of "the decision, England remained outside the Gregorian system for a further 170 years, communications during that period customarily carrying two dates, one 'OS' or Old Style, the other 'NS' or New Style." Thomas Jefferson,for example, lived during the time England eventually converted, so he instructed that his tombstone bear his dates of birth and death in the Old Style and New Style, respectively.^[6] At Jefferson's birth the difference would have been eleven days between styles, had the New Style been converted to yet, as is evidenced by his "original" birthday of April 2 and his New Style birthday of April 13.

Countries that used lunisolar calendars

Japan, Korea, and China started using the Gregorian calendar on 1 January of 1873, 1896, and 1912, respectively.^[7] They had used lunisolar calendars previously. None of them used the Julian calendar; 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. The Arabic numerals may be used for both calendar dates in modern Japanese and Korean languages, but not Chinese.

Japan

Japan started using the Gregorian calendar on 1 January 1873,^[8] locally known as . The preceding day, 31 December 1872, was .
Japan currently employs two calendar systems: Gregorian and modified traditional nengō. Specifically, the months and days now correspond to those of the Gregorian calendar, but the year is expressed as an offset of the era. For example, the Gregorian year 2007 is corresponds to Heisei 19. An era does not necessarily begin on January 1st.

Korea

Korea started using the Gregorian calendar on 1 January 1896, which was the 17th day of the 11th lunar month in not only Korea but also in China that still used the lunisolar calendar.^[9] The lunisolar Korean calendar is now used in very limited unofficial purposes only.

China

The Republic of China started using the Gregorian calendar on 1 January 1912, but the lunisolar Chinese calendar is still used along with the Gregorian calendar, especially when determining certain traditional holidays. The reference has been a longitude of 120°E since 1929, which is also used for Chinese Standard Time (UTC+8). China, Hong Kong, Macao, Singapore and Taiwan all have legal holidays based on the lunisolar Chinese calendar, with the most important one being the Chinese New Year.
To visually distinguish old and new style dates, GB/T 15835-1995, General rules for writing numerals in publications, which is a national standard of the People's Republic of China, requires writing new style dates with Arabic numerals but ''old style dates with Chinese characters, never Arabic numerals''.
In Taiwan, even though new style dates are written in Chinese characters in very formal texts, it is now common to see Arabic numerals in new style dates in less formal texts. When writing old style dates, Chinese characters are usually used while Arabic numerals are considered very casual and strongly discouraged as in Mainland China.

See also

★ British Calendar (New Style) Act 1750

★ Fiscal year

Further reading

★ Details of conversion for many countries

★ Side-by-side Old style–New style reference

★ ''Time to Take Note: The 1752 Calendar Change'' from Ancestry.com

Footnotes

1. At the time, Poland was part of the Russian Empire
2. Nørby, Toke. The Perpetual Calendar: What about England Version 29 February 2000
3. Tuesday 31 December 1661, Pepys Diary "I sat down to end my journell for this year, ..."
4. Russia: The October (November) Revolution
5.
6. Monticello Report: The Calendar and Old Style (O. S.)
7. BAD LINK! Regnal Year Conversion Chart
8. The Japanese Calendar History
9. The Dawn of Modern Korea (266) Lunar Calendar