As we settle into 2015, the start of the New Year has reminded me about a great debate that took place in the Library of the Royal Society back in the summer of 2014. Well, alright, not a great debate, more a gentle chat, on the subject of Robert Hooke’s date of birth. It turned out the confusion was simply down to one source ‘correcting’ for the old calendar date and another not. The change in calendars and the occasional odd recording of a date can cause confusion when conducting research or when attempting to figure out exactly when to celebrate a historical anniversary. Even those of us who should know better sometimes forget!

Before 1752, the legal year in England and Wales began on the 25th March, as opposed to the 1st January (in Scotland the New Year had been on 1 January since 1600). They were using the Julian calendar, but following the Calendar (New Style) Act, the Gregorian calendar was adopted and the New Year was set to begin on the 1st January 1752. The Gregorian calendar was first devised in 1582, and was widely used across Europe by the time the English calendar was changed. In addition to welcoming a new year on the 1st January, 1752 had to be shortened to bring the dates in sync with the Gregorian calendar. In order to do this, 11 days went ‘missing’ from September 1752. Some sources suggest that this caused rioting, and although these may be erroneous the calendar change was unlikely to have had universal support.

This made me curious about the thoughts of Royal Society Fellows about the opposing calendars. Writing to Hans Sloane in 1700, John Wallis wrote to express his views against adopting the Gregorian ‘correction’. Wallis also discusses a letter from Leibniz, in which the use of old and new style dating in Europe is mentioned. In the opening paragraph Wallis states: ‘I think it was very unhappily introduced at first, not only as not perfectly true; but principally, as having caused confusion of stile throughout Christendome’. He then goes on to express why he favours the Julian year. This letter is in our early letters series (ref. EL/W2/66) and is available to view here at the Royal Society Library.


Portrait of John Wallis by Gerard Soest, 17th century © The Royal Society


However by 1752, it is clear that at least one of the Royal Society Fellows supported the change, namely George Parker, 2nd Earl of Macclesfield and President of the Society from November 1752 (shortly after the ‘missing 11 days’) until his death in 1764. Parker was a prominent figure in favour of changing the calendar. He produced a paper on the subject which was published in the Philosophical Transactions volume 46. The paper concentrates on the calculations required by the two calendars, and includes details of ‘a method of finding the time of Easter, as it is observed in most parts of Europe’, noting that should the country choose to adopt the Gregorian calendar, they ought to bring the time for celebrating Easter in line with the majority of Europeans. This of course would go some way to addressing the confusion that so concerned Wallis. Parker went on to speak at the House of Lords in favour of this change in the year, the speech was published and although we do not have a copy here in our collections, it is still available to purchase.


Portrait of George Parker, 2nd Earl of Macclesfield by Thomas Hudson, 1754 © The Royal Society


The Julian and Gregorian calendars were not even the only options available. For example in the Society’s Tracts collection, there is a printed work by ‘H.J’ on the Georgian calendar (ref. Tracts X158/1) – the calendar was accompanied by three essays dedicated to the King, the Earl of Chesterfield and our old friend the Earl of Macclesfield. However I for one am grateful there is only one major change in dating to remember!


Page from ‘The pancronometer, or universal Georgian calendar, adjusted to the Gregorian and Julian accounts’ by ‘H.J,’ 1753


  • Sheridan Williams

    This is why the tax year ends on 5 April rather than 25 March quarter day. Otherwise more tax would have been due.

  • Stefan Janusz

    A great post that will definitely come in useful in answering queries about big anniversaries such as Phil Trans’ 350th birthday – especially with images of the Council minute that kicked it all off doing the rounds (‘well… it was their 1664, but that’s our 1665…’). And an excellent reference in the journal itself! The old system, of course, is memorialised by the beginning of the tax year being on 6 April (tax collectors certainly weren’t happy to lose 11 days) – although reading that Wikipedia entry on this nugget in particular leads me to believe this is more contentious a debate than I first thought!