Old Style and New Style dates
In
Britain and countries of the
British Empire,
Old Style or
O.S. after a date means that the date is in the
Julian calendar, in use in those countries until 1752;
New Style or
N.S. means that the date is in the
Gregorian calendar, adopted on
14 September 1752 (New Style).
For example, 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 Old Style dating in 1616, while
Spain was using New Style. Cervantes actually died ten days before Shakespeare.
Because of the differences, English people and their correspondence often employed two dates, more or less automatically, as Benjamin Woolley observed in his biography of Dr.
John Dee, The Queen's Conjurer, who fought unsuccessfully for England to embrace the 1583/4 date set for the change. It didn't. Wolley 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." (173)
Thomas Jefferson, for example, lived during the time England eventually converted, so his tombstone bore his dates in the Old Style, and noted them as such, at his instruction. By then the difference was greater than ten days.
A further complication is that the start of the
Julian year was not always January 1st but was altered at different times in different countries. For a long time the year in England began on
25 March (
Lady Day), so for example
Elizabeth I of England was recorded as having died on
24 March 1602 (Old Style); this would be written
24 March 1603 in the modern system of numbering years. Although this would correspond to
3 April 1603 if fully converted into the Gregorian calendar, the month and day of a British event are normally not converted. For complete avoidance of ambiguity, historians write dates in the ambiguous part of the year in slashed format, for example "24 March/3 April 1602/1603".
Catholic countries such as
Italy,
Poland,
Spain, and
Portugal were first to change to the Gregorian calendar. Thursday,
1582 October 4 was followed by Friday,
1582 October 15, with ten days "missing". Countries that did not change until the 1700s observed an additional
leap year, necessitating 11 "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; however, the Gregorian calendar was introduced there much later—on
February 14 1918 (New Style). Hence the
October Revolution of 1917 is so called, despite having taken place on
November 7 (New Style), i.e., October 25 (Old Style).
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.
[ Lord Robertson Prospects for NATO - Russian relations(PDF) Page 1, first paragraph]Usually in modern histories, to avoid confusion and to keep dates consistent, the OS dates are mapped onto NS dates with an adjustment for the start of the year to
1 January. For example modern histories all state that
Charles I of England was executed on
30 January 1649. But Parliamentary documents investigating the
regicide during the
Restoration eleven years later all state that the event happened on
30 January 1648.
[House of Commons Journal Volume 8, 9 June, 1660 Regicides.]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 on
9 December 1582 (in France). 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
4 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 ("New Style"). 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, after setting sail from the
Netherlands on
11 November. 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.
Japan,
Korea, and
China started using the Gregorian calendar on
1 January of
1873,
1896, and
1912, respectively. They used
lunisolar calendars before. In these countries, the old style calendars were similar but not all the same. 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.
Arabic numerals may be used for both calendar dates in modern Japanese and Korean languages, but not Chinese.
The lunisolar
Japanese calendar is no longer used except in very limited unofficial purposes, in which case 135° E of
longitude is the modern reference point also used for
Japan Standard Time (
UTC+9), as opposed to
Kyoto as the ancient reference point and national capital.
The lunisolar
Korean calendar is also used in very limited unofficial purposes only.
The lunisolar
Chinese calendar is still used with the Gregorian calendar in China and Taiwan, especially when determining certain traditional holidays. The reference point is 120° E of longitude since 1929, which is also used for
Chinese Standard Time (
UTC+8).
To visually distinguish old and new style dates,
GB/T 15835-1995, General rules for writing numerals in publications, 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.
*
Fiscal year*
Details of conversion for many countries*
Side-by-side Old style - New style reference
