Old Style and New Style dates

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Issue 9198 of The London Gazette , covering the calendar change in Great Britain. The date heading reads: "From Tuesday September 1, O.S. to Saturday September 16, N.S. 1752". The London Gazette 9198.djvu
Issue 9198 of The London Gazette , covering the calendar change in Great Britain. The date heading reads: "From Tuesday September 1, O.S. to Saturday September 16, N.S. 1752".

Old Style (O.S.) and New Style (N.S.) are terms sometimes used with dates to indicate that the calendar convention used at the time described is different from that in use at the time the document was being written. There were two calendar changes in Great Britain and its colonies, which may sometimes complicate matters: the first was to change the start of the year from Lady Day (25 March) to 1 January; the second was to discard the Julian calendar in favour of the Gregorian calendar. [2] [3] [4] Closely related is the custom of dual dating, where writers gave two consecutive years to reflect differences in the starting date of the year, or to include both the Julian and Gregorian dates.

Lady Day Feast of the Annunciation, usually 25 March in the Western liturgical calendar

In the western liturgical year, Lady Day is the traditional name in some English-speaking countries of the Feast of the Annunciation, known in the 1549 Prayer Book of Edward VI and the 1662 Book of Common Prayer as "The Annunciation of the (Blessed) Virgin Mary" but more accurately termed "The Annunciation of our Lord to the Blessed Virgin Mary". It is the first of the four traditional English quarter days. The "(Our) Lady" is the Virgin Mary. The term derives from Middle English, when some nouns lost their genitive inflections. "Lady" would later gain an -s genitive ending, and therefore the name means "(Our) Lady's day". The day commemorates the tradition of archangel Gabriel's announcement to Mary that she would give birth to the Christ.

The Julian calendar, proposed by Julius Caesar in 46 BC, was a reform of the Roman calendar. It took effect on 1 January 45 BC, by edict. It was the predominant calendar in the Roman world, most of Europe, and in European settlements in the Americas and elsewhere, until it was refined and gradually replaced by the Gregorian calendar, promulgated in 1582 by Pope Gregory XIII.

The Gregorian calendar is the calendar used in most of the world. It is named after Pope Gregory XIII, who introduced it in October 1582. The calendar spaces leap years to make the average year 365.2425 days long, approximating the 365.2422-day tropical year that is determined by the Earth's revolution around the Sun. The rule for leap years is:

Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the year 2000 is.


Beginning in 1582, the Gregorian calendar replaced the Julian in Roman Catholic countries. This change was implemented subsequently in Protestant and Orthodox countries, usually at much later dates. In England and Wales, Ireland, and the British colonies, the change to the start of the year and the changeover from the Julian calendar occurred in 1752 under the Calendar (New Style) Act 1750. In Scotland, the legal start of the year had already been moved to 1 January (in 1600), but Scotland otherwise continued to use the Julian calendar until 1752. Thus "New Style" can either refer to the start of year adjustment, or to the adoption of the Gregorian calendar.

Catholic Church Christian church led by the Bishop of Rome

The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with approximately 1.3 billion baptised Catholics worldwide as of 2017. As the world's "oldest continuously functioning international institution", it has played a prominent role in the history and development of Western civilisation. The church is headed by the Bishop of Rome, known as the pope. Its central administration, the Holy See, is in the Vatican City, an enclave within the city of Rome in Italy.

England and Wales Administrative jurisdiction within the United Kingdom

England and Wales is a legal jurisdiction covering England and Wales, two of the four nations of the United Kingdom. ’England and Wales’ forms the constitutional successor to the former Kingdom of England and follows a single legal system, known as English law.

Kingdom of Ireland Historical kingdom on the island of Ireland between 1542 and 1801

The Kingdom of Ireland was a client state of England and then of Great Britain that existed from 1542 until 1800. It was ruled by the monarchs of England and then of Great Britain in personal union with their other realms. The kingdom was administered from Dublin Castle nominally by the King or Queen, who appointed a viceroy to rule in their stead. It had its own legislature, peerage, legal system, and state church.

In Russia, new style dates came into use in early 1918. Other countries in Eastern Orthodoxy adopted new style dating for their civil calendars but most continue to use the Julian calendar for religious use. In English-language histories of other countries (especially Russia), the Anglophone OS/NS convention is often used to identify which calendar is being used when giving a date.

Russia transcontinental country in Eastern Europe and Northern Asia

Russia, officially the Russian Federation, is a transcontinental country in Eastern Europe and North Asia. At 17,125,200 square kilometres (6,612,100 sq mi), Russia is by a considerable margin the largest country in the world by area, covering more than one-eighth of the Earth's inhabited land area, and the ninth most populous, with about 146.77 million people as of 2019, including Crimea. About 77% of the population live in the western, European part of the country. Russia's capital, Moscow, is one of the largest cities in the world and the second largest city in Europe; other major cities include Saint Petersburg, Novosibirsk, Yekaterinburg and Nizhny Novgorod. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a wide range of environments and landforms. From northwest to southeast, Russia shares land borders with Norway, Finland, Estonia, Latvia, Lithuania and Poland, Belarus, Ukraine, Georgia, Azerbaijan, Kazakhstan, China, Mongolia and North Korea. It shares maritime borders with Japan by the Sea of Okhotsk and the U.S. state of Alaska across the Bering Strait. However, Russia recognises two more countries that border it, Abkhazia and South Ossetia, both of which are internationally recognized as parts of Georgia.

Civil calendar

The civil calendar is the calendar, or possibly one of several calendars, used within a country for civil, official or administrative purposes. The civil calendar is almost always used for general purposes by people and private organizations.

Start of the year in the historical records of Britain and its colonies and possessions

Memorial plaque to John Etty in All Saints' Church, North Street, York, recording his date of death as 28 January 170 8/9 Memorial to John Etty (18373251064).jpg
Memorial plaque to John Etty in All Saints' Church, North Street, York, recording his date of death as 28 January 170 8/9

When recording British history it is usual to use the dates recorded at the time of the event, [lower-alpha 1] with the year adjusted to start on 1 January. But the start of the Julian year was not always 1 January, and was altered at different times in different countries (see New Year's Day in the Julian calendar).

From 1155 to 1752, the civil or legal year in England began on 25 March (Lady Day) [5] [6] so for example the execution of Charles I was recorded at the time in parliament as happening on 30 January 1648 (Old Style). [7] In newer English language texts this date is usually shown as "30 January 1649" (New Style). [2] The corresponding date in the Gregorian calendar is 9 February 1649, the date by which his contemporaries in some parts of continental Europe would have recorded his execution.

Charles I of England 17th-century monarch of kingdoms of England, Scotland, and Ireland

Charles I was the monarch over the three kingdoms of England, Scotland, and Ireland from 27 March 1625 until his execution in 1649.

The O.S./N.S. designation is particularly relevant for dates which fall between the start of the "historical year" (1 January) and the official start date, where different. This was 25 March in England, Wales and the colonies until 1752.

During the years between the first introduction of the Gregorian calendar in continental Europe and its introduction in Britain, contemporary usage in England started to change. [4] In Britain 1 January was celebrated as the New Year festival, [8] but the "year starting 25th March was called the Civil or Legal Year, although the phrase Old Style was more commonly used." [4] To reduce misunderstandings about the date, it was normal in parish registers to place a new year heading after 24 March (for example "1661") and another heading at the end of the following December, "1661/62", a form of dual dating to indicate that in the following few weeks the year was 1661 Old Style but 1662 New Style. [9] Some more modern sources, often more academic ones, also use the "1661/62" style for the period between 1 January and 25 March for years before the introduction of the Gregorian calendar in England. (See for example The History of Parliament). [10]

Dual dating

Dual dating is the practice, in historical materials, to indicate some dates with what appears to be duplicate, or excessive digits, sometimes separated by a hyphen or a slash. This is also often referred to as double dating. The need for double dating arose from the transition from an older calendar to a newer one. For example, in "10/21 February 1750/51", the dual day of the month is due to the correction for excess leap years in the Julian calendar by the Gregorian calendar, and the dual year is due to some countries beginning their numbered year on 1 January while others were still using another date.

The History of Parliament project to write a history of the United Kingdom Parliament and its predecessors through biographies of their members

The History of Parliament is a project to write a complete history of the United Kingdom Parliament and its predecessors, the Parliament of Great Britain and the Parliament of England. The history will principally consist of a prosopography, in which the history of an institution is told through the individual biographies of its members. After various amateur efforts the project was formally launched in 1940 and since 1951 has been funded by the Treasury. As of 2010 the volumes covering the House of Commons for the periods 1386–1421, 1509–1629, and 1660–1832 have been completed and published ; research work on the remaining periods and on the House of Lords is ongoing. In 2011 the completed sections were republished on the internet.

Scotland had already partly made the change: its calendar year had begun on 1 January since 1600. [11] [12]

Adoption of the Gregorian calendar

William Hogarth painting: Humours of an Election (c. 1755), which is the main source for "Give us our Eleven Days". William Hogarth 028.jpg
William Hogarth painting: Humours of an Election (c. 1755), which is the main source for "Give us our Eleven Days".

Through the enactment of the British Calendar (New Style) Act 1750 and of the Irish Parliament's Calendar (New Style) Act, 1750, [13] Great Britain, Ireland and the British Empire (including much of what is now the eastern part of 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. Claims that rioters demanded "Give us our eleven days" grew out of a misinterpretation of a painting by William Hogarth. [14] The British tax year traditionally began on Lady Day (25 March) on the Julian calendar and this became 5 April, which was the "New Style" equivalent. [15] A 12th skipped Julian leap day in 1800 changed its start to 6 April. It was not changed when a 13th Julian leap day was skipped in 1900, so the tax year in the United Kingdom still begins on 6 April. [16]

Adoption in the Americas

The European colonies of the Americas adopted the new style calendar when their mother countries did. In what is now the continental United States, the French and Spanish possessions did so before the British colony. In Alaska, the change took place after the United States purchased Alaska from Russia. Friday, 6 October 1867 was followed by Friday, 18 October. Instead of 12 days, only 11 were skipped, and the day of the week was repeated on successive days, because at the same time the International Date Line was moved, from following Alaska's eastern border with Canada to following its new western border, now with Russia. [17]

Anglophone usage describing events in other countries

It is common in English language publications to use the familiar Old Style and/or New Style terms when discussing events and personalities in other countries, especially with reference to the Russian Empire and the very-early Russian Soviet. For example, in 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. [18]

When this usage is encountered, the British adoption date is not necessarily intended. The 'start of year' change and the calendar system change were not always adopted concurrently. Similarly, civil and religious adoption may not have happened at the same time (or even at all). In the case of Eastern Europe, for example, all of these assumptions would be incorrect.

Transposition of historical event dates and possible date conflicts

Thomas Jefferson's tombstone. Written below the epitaph is "Born April 2 1743 O.S. Died July 4 1826" Thomas Jefferson's Grave Site.jpg
Thomas Jefferson's tombstone. Written below the epitaph is "Born April 2 1743 O.S. Died July 4 1826"

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 well 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 using the Gregorian calendar. For example, the Battle of Blenheim is always given as 13 August 1704. However confusion occurs when an event involves 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), in 1688. [19]

The Battle of the Boyne in Ireland took place a few months later on 1 July 1690 (Julian calendar). This maps to 11 July (Gregorian calendar), conveniently close to the Julian date of the subsequent (and more decisive) Battle of Aughrim on 12 July 1691 (Julian). This latter battle was commemorated annually throughout the 18th century on 12 July, [20] following the usual historical convention of commemorating events of that period within Great Britain and Ireland by mapping the Julian date directly onto the modern Gregorian calendar date (as happens for example with Guy Fawkes Night on 5 November). The Battle of the Boyne was commemorated with smaller parades on 1 July. However, the two events were combined in the late 18th century, [20] and continue to be celebrated as "The Twelfth".

Because of the differences, British writers and their correspondents often employed two dates, dual dating, more or less automatically. For this reason, letters concerning diplomacy and international trade sometimes bore both Julian and Gregorian dates to prevent confusion: for example, Sir William Boswell writing to Sir John Coke from The Hague dated a letter "12/22 Dec. 1635". [19] In his biography of Dr John Dee, The Queen's Conjurer, Benjamin Woolley surmises that because Dee fought unsuccessfully for England to embrace the 1583/84 date set for the change, "England remained outside the Gregorian system for a further 170 years, communications during that period customarily carrying two dates". [21] In contrast, Thomas Jefferson, who lived at the time that the British Isles and colonies eventually converted to the Gregorian calendar, instructed that his tombstone bear his date of birth using the Julian calendar (notated O.S. for Old Style) and his date of death using the Gregorian calendar. [22] At Jefferson's birth the difference was eleven days between the Julian and Gregorian calendars; thus his birthday of 2 April in the Julian calendar is 13 April in the Gregorian calendar. Similarly, George Washington is nowadays officially reported as having been born on 22 February 1732, rather than on 11 February 1731/32 (Julian calendar). [23]

There is some evidence that the calendar change was not easily accepted. Many British people continued to celebrate their holidays "Old Style" well into the 19th century, [lower-alpha 2] a practice that according to the author Karen Bellenir reveals a deep emotional resistance to calendar reform. [24]

Differences between Julian and Gregorian dates

The change arose from the realisation that the correct figure for the number of days in a year is not 365.25 (365 days 6 hours) as assumed by the Julian calendar but rather less: the Julian calendar has too many leap years. The consequence was that the basis for calculation of the date of Easter as decided in the 4th century had drifted from reality. The Gregorian calendar reform also dealt with the accumulated difference between these figures, between the years 325 and 1582 (1752 in the British Empire), by skipping 10 days (11 in the case of Great Britain, including its colonies and Ireland) to restore the date of the vernal equinox to approximately 21 March, the approximate date it occurred at the time of the First Council of Nicea in 325.

For a ready reckoner to assist in converting O.S. dates to N.S. and vice versa, see this table.

See also


  1. British official legal documents of the 16th and 17th centuries were usually dated by the regnal year of the monarch. As these commence on the day and date of the monarch's accession, they normally span two consecutive calendar years and have to be calculated accordingly, but the resultant dates should be unambiguous.
  2. See also Little Christmas.
  1. Gazette 9198.
  2. 1 2 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.
  3. 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 1); and that the 'Leap Year' change should be described as the change from Julian to Gregorian."
  4. 1 2 3 Spathaky, Mike Old Style and New Style Dates and the change to the Gregorian Calendar. "Before 1752, 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 Historical Year 1734 started even though the Civil Year 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 Civil or the Historical Year. 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."
  5. Nørby, Toke. The Perpetual Calendar: What about England? Version 29 February 2000.
  6. Gerard 1908.
  7. "House of Commons Journal Volume 8, 9 June 1660 (Regicides)". British History Online. Retrieved 18 March 2007.
  8. Tuesday 31 December 1661, Pepys Diary "I sat down to end my journell for this year, .."
  9. Spathaky, Mike Old Style and 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, thus: . Very occasionally a hyphen is used, as 1733-34."
  10. See for example this biographical entry: Lancaster, Henry (2010). "Chocke, Alexander II (1593/4-1625), of Shalbourne, Wilts.; later of Hungerford Park, Berks". In Thrush, Andrew; Ferris, John P. The History of Parliament: the House of Commons 1604-1629, ed. Andrew Thrush and John P. Ferris, 2010 Available from Cambridge University Press. Cambridge University Press.
  11. Steele 2000, p. 4.
  12. Bond 1875, See footnote on pages xvii–xviii: original text of the Scottish decree.
  13. Parliament of Ireland 1750.
  14. Poole 1995 , pp. 95–139.
  15. Cheney & Jones 2000 , p. 18
  16. Philip 1921, p. 24.
  17. Dershowitz, Nachum; Reingold, Edward M. (2008). Calendrical Calculations. Cambridge: Cambridge University Press. p. 47. ISBN   9780521885409.
  18. EB online 2017.
  19. 1 2 Cheney & Jones 2000 , p. 19.
  20. 1 2 Lenihan, Pádraig (2003). 1690 Battle of the Boyne. Stroud, Gloucestershire: Tempus. pp. 258–259. ISBN   0 7524 2597 8.
  21. Baker, John. "Why Bacon, Oxford and Other's Weren't Shakespeare". Archived from the original on 4 April 2005.) uses this quote by Benjamin Woolley and cites The Queen's Conjurer, The Science and Magic of Dr. John Dee, Adviser to Queen Elizabeth I, page 173.
  22. "Old Style (O.S.)". monticello.org. June 1995. Retrieved 6 May 2017.
  23. Engber, Daniel (18 January 2006). "What's Benjamin Franklin's Birthday?". Slate . Retrieved 8 February 2013. (Both Franklin's and Washington's confusing birth dates are clearly explained).
  24. Bellenir, Karen (2004). Religious Holidays and Calendars. Detroit: Omnigraphics. p. 33.

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Swedish calendar used in Sweden and Finland between 1700 and 1712

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The Calendar Act 1750 (c.23) was an Act of the Parliament of Great Britain. The Act had two parts: first, it reformed the calendar of England and the British Dominions so that the new legal year began on 1 January rather than 25 March ; and, second, Great Britain and its Dominions adopted the Gregorian calendar, as already used in most of western Europe.

The proleptic Gregorian calendar is produced by extending the Gregorian calendar backward to dates preceding its official introduction in 1582. In countries that adopted the Gregorian calendar later, dates occurring in the interim are sometimes "Gregorianized" as well. For example, George Washington was born on February 11, 1731, as Great Britain and its possessions were using the Julian calendar with English years starting on March 25 until September 1752. After the switch, that day became February 22, 1732, which is the date commonly given as Washington's birthday.

The following is a list of the official regnal years of the monarchs of the Kingdom of England, Kingdom of Great Britain and United Kingdom from 1066. The regnal calendar is used in many official British government and legal documents of historical interest, notably parliamentary statutes.

This is the calendar for Old Style 1751, which began on Monday, 25 March, in England. The Old Style year 1751 ended on 31 December, unlike England's typical Old Style calendar, which ended with the following March, on 24 March. Hence, 1751 was the final year to begin on 25 March, and Old Style 1752 began on 1 January (Wednesday), in England, Wales, Ireland, or the American colonies (etc.), as a transition year to the New Style (N.S.) Gregorian calendar. However, both calendars had been in dual use in some regions, for many years.

This is the calendar for Old Style 1752, a leap year which began on 1 January, and dropped 3–13 September to transition to the Gregorian calendar. Previously, the Old Style calendar in England had begun on 25 March and ended with the following March, on 24 March. Because the Gregorian calendar did not have leap day in 1700, the original 10-day difference in calendars had expanded to an 11-day difference, and to compensate, 2 September was followed by 14 September, as skipping 11 days beyond 3 September. Year 1753, in England followed the full Gregorian calendar. Note, below, the shortened length of September.

Adoption of the Gregorian calendar

The adoption of the Gregorian Calendar was an event in the modern history of most nations and societies, marking a change from their traditional dating system to the modern dating system that is widely used around the world today. Some countries adopted the new calendar from 1582, some did not do so before the early twentieth century, and others did so at various dates between; however a number continue to use a different civil calendar. For many the new style calendar is only used for civil purposes and the old style calendar remains used in religious contexts. Today, the Gregorian calendar is the world's most widely used civil calendar. During – and for some time after – the change between systems, it has been common to use the terms Old Style and New Style when giving dates, to indicate which calendar was used to reckon them.