11 Numbers and dates
The following section offers brief guidance for those working with some less familiar calendars; fuller explanation may be found in Bonnie Blackburn and Leofranc Holford-Strevens, The Oxford Companion to the Year (Oxford University Press, 1999).
Dates in non-Western calendars should be given in the order day, month, year, with no internal punctuation: 25 Tishri am 5757, 13 Jumada I ah 1417. Do not abbreviate months even in notes.
11.8.2 Old and New Style
The terms Old Style and New Style are applied to dates from two different historical periods. In 1582 Pope Gregory XIII decreed that, in order to correct the calendar then used—the Julian calendar—the days 5–14 October of that year should be omitted and no future centennial year (e.g. 1700, 1800, 1900) should be a leap year unless it was divisible by 400 (for example 1600, 2000). This reformed Gregorian calendar was quickly adopted in Roman Catholic countries, more slowly elsewhere: in Britain not till 1752 (when the days 3–13 September were omitted), in Russia not till 1918 (when the days 16–28 February were omitted). Dates in the Julian calendar are known as Old Style, while those in the Gregorian are New Style.
Until the middle of the eighteenth century not all states reckoned the new year from the same day: whereas France adopted 1 January from 1563, and Scotland from 1600, England counted from 25 March in official usage as late as 1751. Thus the execution of Charles I was officially dated 30 January 1648 in England, but 30 January 1649 in Scotland. Furthermore, although both Shakespeare and Cervantes died on 23 April 1616 according to their respective calendars, 23 April in Spain (and other Roman Catholic countries) was only 13 April in England, and 23 April in England was 3 May in Spain.
Confusion is caused on account of the adoption, in England, Ireland, and the American colonies, of two reforms in quick succession: the adoption of the Gregorian calendar and the change in the way the beginning of the year was dated. The year 1751 began on 1 January in Scotland and on 25 March in England, but ended throughout Great Britain and its colonies on 31 December, so that 1752 began on 1 January. So, whereas 1 January 1752 corresponded to 12 January in most Continental countries, from 14 September onwards there was no discrepancy. Many writers treat the two reforms as one, using Old Style and New Style indiscriminately for the start of the new year and the form of calendar. In the interests of clarity Old Style should be reserved for the Julian calendar and New Style for the Gregorian; the 1 January reckoning should be called ‘modern style’, that from 25 March ‘Annunciation’ or ‘Lady Day’ style.
It is customary to give dates in Old or New Style according to the system in force at the time in the country chiefly discussed. Any dates in the other style should be given in parentheses with an equals sign preceding the date and the abbreviation of the style following it: 23 August 1637 NS (= 13 August OS) in a history of England, or 13 August 1637 OS (= 23 August NS) in one of France. In either case, 13/23 August 1637 may be used for short. On the other hand, it is normal to treat the year as beginning on 1 January: modern histories of England date the execution of Charles I to 30 January 1649. When it is necessary to keep both styles in mind, it is normal to write 30 January 1648/9; otherwise the date should be given as 30 January 1648 (= modern 1649).
11.8.3 Greek calendars
In the classical period years were designated by the name of a magistrate or other office-holder, which meant nothing outside the city concerned. In the third century bc a common framework for historians was found in the Olympiad, or cycle of the Olympic Games, held in the summer every four years from 776 bc onwards. Thus 776/5 was designated the first year of the first Olympiad; 775/4 the second year; and 772/1 the first year of the second Olympiad. When modern scholars need to cite these datings, they are written Ol. 1, 1, Ol. 1, 2, and Ol. 2, 1 respectively.
11.8.4 French Republican calendar
The Republican calendar was introduced on 5 October 1793, and was discontinued with effect from 1 January 1806. On its introduction it was antedated to begin from the foundation of the Republic (22 September 1792). The months of the new calendar were named according to their seasonal significance. Though difficult to translate, approximations are included in parentheses:
germinal (seed time)
The months are not now capitalized in French, though they were at the time and may still be so in English. Years of the Republican calendar are printed in capital Roman numerals: 9 thermidor An II; 13 vendémiaire An IV; in English Year II, Year IV.
11.8.5 Jewish calendar
The Jewish year consists in principle of twelve months of alternately 30 and 29 days; in seven years out of nineteen an extra month of 30 days is inserted, and in some years either the second month is extended to 30 days or the third month shortened to 29 days. The era is reckoned from a notional time of Creation at 11.11 and 20 seconds p.m. on Sunday, 6 October 3761 bc.
11.8.6 Muslim calendar
The Muslim year consists of twelve lunar months, so that thirty-three Muslim years roughly correspond to thirty-two Christian ones. Years are counted from the first day of the year in which the Prophet made his departure, or Hegira, from Mecca to Medina, namely Friday, 16 July ad 622.