Vanadium 50 said:
The offset is only eleven days, though.
Yes, but, note the example on dates before 1752.
In the case of Isaac Newton, his death date is given as 20 March 1726/27.
From Lancashire Parish Clerks Online:
To avoid any ambiguity, we record dates between 1 Jan and 24 Mar of each year prior to 1752 as dual dates. So for example, 31 Dec 1746 is followed by 1 Jan 1746/7, 2 Jan 1746/7 and so on until 24 Mar 1746/7, then 25 Mar 1747.
In a Wikipedia article, a note on Newton's birth date:
Isaac Newton was born (according to the
Julian calendar in use in England at the time) on Christmas Day, 25 December 1642 (
NS 4 January 1643)
and
https://en.wikipedia.org/wiki/Isaac_Newton#cite_note-OSNS-5
During Newton's lifetime, two calendars were in use in Europe: the
Julian ("
Old Style") calendar in
Protestant and
Orthodox regions, including Britain; and the
Gregorian ("
New Style") calendar in Roman Catholic Europe. At Newton's birth, Gregorian dates were ten days ahead of Julian dates; thus, his birth is recorded as taking place on 25 December 1642 Old Style, but it can be converted to a New Style (modern) date of 4 January 1643. By the time of his death, the difference between the calendars had increased to eleven days. Moreover, he died in the period after the start of the New Style year on 1 January but before that of the Old Style new year on 25 March. His death occurred on 20 March 1726, according to the Old Style calendar, but the year is usually adjusted to 1727. A full conversion to New Style gives the date 31 March 1727.
I encounter this mess when trying to determine birth/baptisms, marriages and deaths of ancestors from England, Scotland, Wales and Ireland prior to 1752.
In a summary of Newton's early life, while at the University of Cambridge.
In 1665, he discovered the generalised
binomial theorem and began to develop a mathematical theory that later became
calculus. Soon after Newton obtained his BA degree at Cambridge in August 1665, the university temporarily closed as a precaution against the
Great Plague.
https://en.wikipedia.org/wiki/Isaac_Newton#Early_life
By September 1664, Newton had started to use some of the pages for the optical and mathematical calculations, inspired by Descartes and van Schooten, that were beginning to occupy him (see
Add. 3996 and Fitzwilliam Museum, MS. 1-1936). Over the next two years, Newton broadened his reading only slightly. Nevertheless, through the study of Wallis’ works and of the other authors (Johann Hudde, Hendrick van Heuraet, and Jan de Witt) whose writings were presented by van Schooten in his edition of Descartes’
Geometria (1639-41), Newton gradually mastered the analysis of curved lines, surfaces, and solids. He learned how to use the method of infinite series and extended it by discovering how to expand binomials with fractional indices. Most significantly, he developed an approach to the measurement of curved lines that mapped the motion that produced them. This arose out of dissatisfaction with the method of infinitesimals and the advances towards describing curves through their tangents that Newton had made with it. By autumn 1665, Newton had worked out a method for replacing the use of infinitesimal increments of space in his calculations with instantaneous changes in the velocity of a moving point by which curved lines were described. Stimulated entirely by his reading, Newton had invented the method of fluxions, or calculus, through the working in his ‘Waste Book’
https://cudl.lib.cam.ac.uk/view/MS-ADD-04004/1
In another summary,
https://fee.org/articles/how-isaac-...from-the-great-plague-into-a-year-of-wonders/
Away from university life, and unbounded by curriculum constraints and professor’s whims, Newton dove into discovery. According to
The Washington Post: “Without his professors to guide him, Newton apparently thrived.” At home, he built bookshelves and created a small office for himself, filling a blank notebook with his ideas and calculations. Absent the distractions of typical daily life, Newton’s creativity flourished. During this time away he discovered differential and integral calculus, formulated a theory of universal gravitation, and explored optics, experimenting with prisms and investigating light.
So, during 1665 through 1666, Newton was developing what became 'calculus'.
Interstingly, U of Cambridge has his date of his BA as 1664/5
https://venn.lib.cam.ac.uk/cgi-bin/...ll&tex=NWTN661I&sye=&eye=&col=all&maxcount=50
Apparently, the answer to the OP's question can be found in the following publication by Cambridge University Press.
Whiteside, D.T., ed. (1967). "Part 7: The October 1666 Tract on Fluxions".
The Mathematical Papers of Isaac Newton.
1. Cambridge University Press.
https://www.cambridge.org/us/univer...-newton-volume-1?format=PB&isbn=9780521045957
The bringing together, in an annotated and critical edition, of all the known mathematical papers of Isaac Newton marks a step forward in the publication of the works of this great natural philosopher. In all, there are eight volumes in this present edition. Translations of papers in Latin face the original text and notes are printed on the page-openings to which they refer, so far as possible. Each volume contains a short index of names only and an analytical table of contents; a comprehensive index to the complete work is included in Volume VIII. Volume I covers three exceptionally productive years: Newton's final year as an undergraduate at Trinity College, Cambridge, and the two following years, part of which were spent at his home in Lincolnshire on account of the closure of the university during an outbreak of bubonic plague.
There are 8 volumes sold separately.
https://www.cambridge.org/us/univer...e/series/mathematical-papers-sir-isaac-newton
and one can buy the 8 volume set
https://www.cambridge.org/us/univer...ts/mathematical-papers-isaac-newton?format=WX
Perhaps we can acknowledge the contributions of both men, which didn't happen in a vacuum.
https://www.ams.org/notices/200905/rtx090500602p.pdf
In his review of the book, The Calculus Wars: Newton, Leibniz, and the Greatest Mathematical Clash of All Time by Jason Socrates Bardi (Basic Books, 2007), professor Brian Blank writes:
There is no doubt that Newton’s discoveries preceded those of Leibniz by nearly a decade. Stimulated by the Lucasian Lectures Isaac Barrow delivered in the fall of 1664, Newton developed his calculus between the winter of 1664 and October 1666. Two preliminary manuscripts were followed by the so-called October 1666 tract, a private summation that was not printed until 1962. Because of Newton’s dilatory path to publication, word of his calculus did not spread beyond Cambridge until 1669. In that year, Newton, reacting to the rediscovery of his infinite series for log(1 + x), composed a short synopsis of his findings, the De analysi per aequationes numero terminorum infinitas. The De analysi was written near the end of an era in which scientific discoveries were often first disseminated by networking rather than by publication. Henry Oldenburg, Secretary of the Royal Society, and John Collins, government clerk and de facto mathematical advisor to Oldenburg, served as the principal hubs of
correspondence in England. Dispatched by Barrow on behalf of a “friend of mine here, that hath a very excellent genius,” the De analysi reached Collins in the summer of 1669. “Mr. Collins was very free in communicating to able Mathematicians what he had receiv’d,” Newton later remarked.
Someone else's commentary on Newton's achievements
https://plato.stanford.edu/entries/newton/#NewYeaCamPriPri
By 1664, Newton had begun reaching beyond the standard curriculum, reading, for example, the 1656 Latin edition of Descartes's Opera philosophica, which included the Meditations, Discourse on Method, the Dioptrics, and the Principles of Philosophy. By early 1664 he had also begun teaching himself mathematics, taking notes on works by Oughtred, Viète, Wallis, and Descartes— the latter via van Schooten's Latin translation, with commentary, of the Géométrie. Newton spent all but three months from the summer of 1665 until the spring of 1667 at home in Woolsthorpe when the university was closed because of the plague. This period was his so-called annus mirabilis.
That seems like ~1.5 years (August 1665 through ~March/April 1667)
It is difficult to know which Calendar folks are using, but I often expect the later Gregorian calendar in writings after 1752.
Let's not forget René Descartes (1596–1650)
https://plato.stanford.edu/entries/descartes/
