Editing Old Style and New Style dates (section)

{{Short description|Changes in calendar conventions}}
{{Redirect2|Old Style|New Style|other meanings of old style|Old Style (disambiguation)|other meanings of new style|The New Style (disambiguation){{!}}The New Style}}
{{about|the 18th-century changes in calendar conventions used by Great Britain and its colonies, together with a brief explanation of usage of the term in other contexts|a more general discussion of the equivalent transitions in other countries|Adoption of the Gregorian calendar}}
{{Use dmy dates|date=May 2021}}
[[File:The London Gazette 9198.djvu|thumb|Issue 9198 of ''[[The London Gazette]]'', covering the calendar change in Great Britain. The issue spans the changeover; the date heading reads: "From Tuesday September 1, O.S. to Saturday September 16, N.S. 1752".<ref>{{cite journal |journal=London Gazette |issue=9198 |page=1 |date=1 September 1752 |title= The London Gazette {{!}} From Tuesday September 1 O.S. to Saturday September 16 N.S. 1752 |url=https://www.thegazette.co.uk/London/issue/9198/page/1}}</ref>]]
'''Old Style''' ('''O.S.''') and '''New Style''' ('''N.S.''') indicate dating systems before and after a calendar change, respectively. Usually, they refer to the change from the [[Julian calendar]] to the [[Gregorian calendar]] as enacted in various [[Europe|European]] countries between 1582 and 1923. <!-- Similar notations in Asia are outside the scope of this article. -->

In [[England]], [[Wales]], [[Ireland]] and [[British America|Britain's American colonies]], there were two calendar changes, both in 1752. The first adjusted the start of a new year from 25 March ([[Lady Day]], the [[Feast of the Annunciation]]) to 1 January, a change which [[Scotland]] had made in 1600. The second discarded the Julian calendar in favour of the Gregorian calendar, skipping 11 days in the month of September to do so.{{sfn|Poole|1995 |pages=95–139}}<ref name="MS2">{{cite web |last=Spathaky |first=Mike |url=https://www.cree.name/genuki/dates.htm |title=Old Style and New Style Dates and the change to the Gregorian Calendar |access-date=19 August 2023}}. "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."</ref>  To accommodate the two calendar changes, writers used [[dual dating]] to identify a given day by giving its date according to both styles of dating.

For countries such as [[Russia]] where no start-of-year adjustment took place,{{efn|By decrees (1735, 1736) of [[Peter the Great]] in December 1699 (with effect from 1 January 1700), Russia changed its start of year from September to January and adopted the AD era in place of [[Anno Mundi]].<ref>{{cite book |title=Полное собрание законов Российской империи. Том III |trans-title=Complete Collection of Laws of the Russian Empire. Volume III. |page=682  |entry=Ukase No. 1735 |entry-url=https://viewer.rsl.ru/ru/rsl01003821638?page=682&rotate=0&theme=white |date=10 December 1699 }}</ref><ref name="Ukase 1736">{{cite book |title=Полное собрание законов Российской империи. Том III |trans-title=Complete Collection of Laws of the Russian Empire. Volume III. |page=683  |entry=Ukase No. 1736 |entry-url=https://viewer.rsl.ru/ru/rsl01003821638?page=683&rotate=0&theme=white |date=20 December 1699 }}</ref>}} O.S. and N.S. simply indicate the Julian and Gregorian dating systems respectively.