Calendar Reform in England, 1752

This change was as a result of an Act of Parliament - the "Calendar Act" of 1751 An Act for Regulating the Commencement of the Year; and for Correcting the Calendar now in Use.

What isn't so widely known is a second change which the Act introduced - as named in the first part of the Act's title. The Act changed the first day of the year (or, if you want to impress your friends with a new word, the Supputation of the Year).

Prior to 1752 in England, the year began on 25 March (Lady Day). Lady Day is one of the Quarter Days, which are still used in legal circles. The Quarter Days divide the year in quarters (hence the name :-), and the Quarter Days are: Lady Day (25 March), Midsummers Day (24 June), Michaelmas Day (29 September), and Christmas Day (25 December).

So, in England, the day after 24 March 1642 was 25 March 1643. The Act changed this, so that the day after 31 December 1751 was 1 January 1752. As a consequence, 1751 was a short year - it ran only from 25 March to 31 December.
To throw some more confusion on the issue, Scotland had changed the first day of the year to 1 January in 1600 (in 1600, Scotland was a separate kingdom). When King James VI of Scotland became also King James I of England in 1603, the possibilities of date confusion must have been very large.

Historians have to be on their toes with dates prior to 1752. For example, in The Tower of London there is some graffiti scratched into a cell wall by someone imprisoned in January 1642 for his role in the Battle of Edgehill (which took place on 23 October 1642).

Some unanswered questions

• There is considerable evidence of contemporary dual dating. For example, some essentially contemporary paintings of the execution of King Charles I on Tuesday 30 January 1648 have a title bearing the date 30 January 1648/9. Samuel Pepys's diary begins on New Years Day (1 January) 1660, but it is clear that this is actually the year 1659/60. So was the Calendar Act in 1751 merely formalising common usage, or was it a radical change ? The preface to one modern book of Samuel Pepys's diary states that using 1 January as the start of the year was common practice at that time - i.e. 1660.
  I've seen a pamphlet at Broughton Castle which refers to a speech made on Thursday 27 January 1658 - and the pamphlet states it was printed in 1659. In order for the day to be a Thursday, this must be referring to 27 January 1658/9 (i.e. the pamphlet was printed some months after the speech), however the year is specified as 1658 - and not as 1658/9.
  So the year was commencing on 25 March in 1658, but on 1 January in 1660 ?
  Perhaps the answer is connected with the coronation of King Charles II in Scotland on 1 January 1651 - that's a Scottish date, for a Scottish king. Perhaps the Royalist cause used 'Scottish' dates, and the Parliamentarian cause used 'old style' dates ? Although this theory maybe doesn't sit well with the fact that from 1654 Pepys had been steward to Edward Mountagu, a General-at-Sea in Cromwell's Protectorate...
  King Charles II did not become king of England until 8 May 1660 (coronation on 23 April 1661), after the start of Samuel Pepys's diary.

Leap Years in the Julian Calendar

But remember that 29 February was in the last quarter of the year by the old reckoning.

It appears that leap years were those where the year number was one less than an exact multiple of 4! The House of Commons Journal for Wednesday, February 29th, 1659 would seem to bear this out - remembering that this date is otherwise expressed as 29 February 1659/60, and appears in Samuel Pepys's diary as 29 February 1660 (just to add to the confusion).
House of Commons Journal for Thursday, 29 February 1643 (otherwise 29 February 1643/4) and House of Commons Journal for Tuesday, 29 February 1647 (otherwise 29 February 1647/8) confirm this, although note the Latin form of the dates which was presumably dropped in the Commonwealth/Protectorate.

The Tax Year