1751 - The Nine Month Year and 1752 - the year they stole 11 days
Before 1751 the UK worked by the Julian calendar (25th March, Lady Day, to 24th March). By this time most of Europe, with the exception of Russia, had switched to the Gregorian calendar (1st January to 31st December).
In 1751 there was a nine month year from 25th March to 31st December. In addition by this time the Julian and Gregorian calendars were 11 days different so in the UK these days were omitted from September 1752; 2nd September was followed by the 14th.
1752 was therefore the first year using the Gregorian calendar in the UK. However, banks ignored the calendar change so the financial year to this day ends on 5th April (11 days after 25th March).
(Source: "Ancestral Trails: The Complete Guide to British Genealogy and Family History" by Mark D. Herber)
Regnal Years
Historic documents often quote the year as being the Xth year in the reign of the king or queen. This method of dating documents was used by Parliament right up to the 1960s. So if a document shows the date as 23 Sept 13 George III this would be 23 Sep 1773 as the 13th occurance of the 23 Sept in the reign of George III was in 1773.
The dates used in the table below are all new style dates. See calendar change for more information about old and new style dates.
| Monarch | Start | End | |
| William I | 25 Dec 1066 | 09 Sep 1087 | |
| William II | 26 Sep 1087 | 02 Aug 1100 | |
| Henry I | 05 Aug 1100 | 01 Dec 1135 | |
| Stephen | 22 Dec 1135 | 25 Oct 1154 | |
| Henry II | 19 Dec 1154 | 06 Jul 1189 | |
| Richard I | 03 Sep 1189 | 06 Apr 1199 | |
| John1 | 27 May 1199 | 1216 | |
| Henry III | 28 Oct 1216 | 16 Nov 1272 | |
| Edward I | 20 Nov 1272 | 07 Jul 1307 | |
| Edward II | 07/08 Jul 1307 | 20 Jan 1327 | |
| Edward III | 24/25 Jan 1327 | 21 Jun 1377 | |
| Richard II | 21/22 Jun 1377 | 29/30 Sep 1399 | |
| Henry IV | 30 Sep 1399 | 20 Mar 1413 | |
| Henry V | 20/21 Mar 1413 | 31 Aug 1422 | |
| Henry VI | 31 Aug / 01 Sep 1422 | 04 Mar 1461 | |
| Edward IV | 04 Mar 1461 | 02 Oct 1470 | |
| Henry VI | 05 Oct 1470 | 11 Apr 1471 | |
| Edward IV | 11 Apr 1471 | 09 Apr 1483 | |
| Edward V | 09 Apr 1483 | 25 Jun 1483 | |
| Richard III | 26 Jun 1483 | 22 Aug 1485 | |
| Henry VII | 22 Aug 1485 | 21 Apr 1509 | |
| Henry VIII | 21/22 Apr 1509 | 28 Jan 1547 | |
| Edward VI | 28 Jan 1547 | 06 Jul 1553 | |
| Jane | 06 Jul 1553 | 19 Jul 1553 | |
| Mary I | 19 Jul 1553 | 24 Jul 1554 | |
| Philip & Mary I2 | 25 Jul 1554 | 17 Nov 1558 | |
| Elizabeth I | 17 Nov 1558 | 24 Mar 1603 | |
| James I | 24 Mar 1603 | 27 Mar 1625 | |
| Charles I | 27 Mar 1625 | 30 Jan 1649 | |
| Oliver Cromwell, Lord Protector | 16 Dec 1653 | 03 Sep 1658 | |
| Richard Cromwell, Lord Protector | 03 Sep 1658 | 07 May 1659 | |
| Charles II3 | 30 Jan 1649 | 06 Feb 1685 | |
| James II | 06 Feb 1685 | 11/23 Dec 1688 | |
| William III & Mary II4 | 13 Feb 1689 | 27 Dec 1694 | |
| William III4 | 27 Dec 1694 | 08 Mar 1702 | |
| Anne | 08 Mar 1702 | 01 Aug 1714 | |
| George I | 01 Aug 1714 | 11 Jul 1727 | |
| George II5 | 11 Jun 1727 | 25 Oct 1760 | |
| George III6 | 25 Oct 1760 | 29 Jan 1820 | |
| George IV | 29 Jan 1820 | 26 Jun 1830 | |
| William IV | 26 Jun 1830 | 20 Jun 1837 | |
| Victoria | 20 Jun 1837 | 22 Jan 1901 | |
| Edward VII | 22 Jan 1901 | 06 May 1910 | |
| George V | 06 May 1910 | 20 Jan 1936 | |
| Edward VIII | 20 Jan 1936 | 11 Dec 1936 | |
| George VI | 11 Dec 1936 | 06 Feb 1952 | |
| Elizabeth II | 06 Feb 1952 | current |
Where more than one date is stated for an event this is because sources used quote differing dates.
1John's regnal years are complicated because early regnal dates were taken from the date the monarch was crowned not the date of accession. John was crowned on Ascension Day which is a movable feast. His subsequent regnal years were not taken from the date of Ascension Day in the year he was crowned but in the current year. Therefore the start date of each regnal year changed. This could cause some dates to appear twice in one regnal year and not at all in an adjoining year.
2add note about Philip and Mary regnal years
3Charles II was restored to the throne in May 1660 (sources quote 08th and 29th). His regnal years were allocated assuming he succeeded his father after his execution on 30 Jan 1649. During the Commonwealth Period (the Interregnum) the regnal system of dating was not used.
4 After Mary died William's regnal years were counted from their joint accession on 13 Feb 1689
5During the reign of George II in 1752 the calendar was changed from the Gregorian to the Julian Calendar. Therefore the first 25 years of George II would be recorded as expected e.g. 01 Dec 20 George II would be 01 Dec 1747. The 26th year of his reign ran from 11 Jun 1752 to 21 Jun 1753 (to adjust for the missing days in Sept 1752). The 27th year ran from 22 Jun 1753 to 21 Jun 1754.
6 The regnal years ignored the Regency period from 06 Feb 1811 to 29 Jan 1820