Chronology of events:

For some events, the year is certain but the month and day are not. Example: We know only the year for the collections of Leeuwenhoek's letters published in Dutch during his lifetime.

For other events, the season or month are certain but the day is not. Example: Leeuwenhoek mentions that someone visited him "last month".

On the other hand, many events did indeed happen on the first day of a month. Example: public appointments to Delft's city offices took effect on January 1 of each year. Thus:

  • A date of January 1 in a given year may indicate that the year is certain but the month and day are not.
  • A date of 1 in a given month may indicate that the year and month are certain but the day is not.

Unless otherwise indicated, for events in England, the date given is Old Style, 10 days behind the Dutch Republic's New Style until 1700 and then 11 days behind.

Date
October 30, 1676 Wrote Letter L-043 of 1676-10-30 to Henry Oldenburg about his discussions with Grew and Boyle as well as the unreliability of the postal system
October 31, 1676 Constantijn Huygens wrote Letter L-044 to Leeuwenhoek about his son Christiaan's translating Letter L-040
November 7, 1676 Wrote Letter L-045 of 1676-11-07 to Constantijn Huygens summarizing the observations of little animals in Letter L-040
November 12, 1676 Henry Oldenburg wrote Letter L-046 to Leeuwenhoek that he would write at greater length soon
November 18, 1676 Visited by Gottfried Leibniz
November 25, 1676 Magistrates approved payment by Maria Thins so Leeuwenhoek could pay Vermeer's creditors
November 27, 1676 Wrote Letter L-047 of 1676-11-27 to Henry Oldenburg, now lost
January 1, 1677 Theodore Craanen wrote Letter L-048 to Leeuwenhoek, some time in 1677, requesting that his relative Johan Ham be allowed to visit
January 1, 1677 Wrote Letter L-049 of some time in 1677 to Robert Boyle, now lost
January 22, 1677 mentor Jacob Spoors buried
January 26, 1677 Constantijn Huygens wrote to Oldenburg about Leeuwenhoek, a "painstaking man" who should be "cherished"
January 30, 1677 cousin Lambrecht Huijchs Leeuwenhoek (1624-1701) bought Buitenwatersloot 214
February 2, 1677 Recovered twenty-six paintings from Jannetje Stevens to help pay Catherine Bolnes' creditors
February 9, 1677 Christiaan Huygens wrote Letter L-050 of 1677-02-09 to Leeuwenhoek that his observations of little animals in spice infusions were well received in France
February 11, 1677 The Royal Society read the first part of Leeuwenhoek's long Letter L-040 of the previous 9 October about little animals in various waters
February 15, 1677 Wrote Letter L-051 of 1677-02-15 to Christiaan Huygens to thank him for translating a letter into French
February 18, 1677 The Royal Society read the second part of Leeuwenhoek's long letter of 9 October 1676
February 22, 1677 Henry Oldenburg wrote Letter L-052 to Leeuwenhoek for more details about his method for observing little animals
March 4, 1677 Henry Oldenburg wrote Letter L-053 to Leeuwenhoek requesting that he examine muscle fibers and brains
March 8, 1677 Named quartermaster of the 2nd quarter
March 8, 1677 The Royal Society read the third part of Leeuwenhoek's long letter of 9 October 1676
March 12, 1677 Maria Thins filed a legal action to prevent Leeuwenhoek from selling The Art of Painting
March 15, 1677 Organized the auction of Vermeer's remaining paintings
March 23, 1677 Wrote Letter L-054 of 1677-03-23 to Henry Oldenburg about the quantity of little creatures in one drop of water
March 25, 1677 The Royal Society published Michael Butterfield's letter about melting glass to make spherical lenses
March 25, 1677 The Royal Society published part of Leeuwenhoek's Letter L-040 of 9 October 1676 reporting little animals in infusions
April 15, 1677 The Royal Society read Leeuwenhoek's Letter L-054 of 23 March 1677 and assigned Grew to replicate his results
April 20, 1677 Henry Oldenburg wrote Letter L-055 to Leeuwenhoek relaying the compliments of the members of the Royal Society
May 14, 1677 Wrote Letter L-056 of 1677-05-14 to Henry Oldenburg about muscles, blood, the movement of fluids in fruit, moxa, and cotton
May 18, 1677 Benedict Haan and Henry Cordes wrote to the Royal Society attesting to the number of little animals in Leeuwenhoek's infusions
May 27, 1677 The Royal Society read Leeuwenhoek's Letter L-056 of 14 May 1677
June 2, 1677 Robbert Gordon wrote to the Royal Society attesting to the number of little animals in Leeuwenhoek's infusions
August 7, 1677 Henry Oldenburg wrote Letter L-057 to Leeuwenhoek, asking him to examine the skin of Moors and enclosing Philosophical Transactions no. 136
August 13, 1677 Aldert Hodenpijl wrote to the Royal Society attesting to the number of little animals in Leeuwenhoek's infusions
August 21, 1677 Johannes Boogert, Robert Poitevin, and W. van der Burch wrote to the Royal Society attesting to the number of little animals in Leeuwenhoek's infusions
August 30, 1677 Alex Petrie wrote to the Royal Society attesting to the number of little animals in Leeuwenhoek's infusions
September 5, 1677 mentor Henry Oldenburg died in London
September 11, 1677 Visited by Hennig Brand, the Hamburg merchant who discovered phosphorus
October 1, 1677 Denis de Dodart wrote to Christiaan Huygens about his admiration for Leeuwenhoek: "people of this merit should be pensioned as external academicians"
October 5, 1677 Wrote Letter L-058 of 1677-10-05 to Henry Oldenburg about skin, eels, fleas, and measuring and counting the little animals; enclosed testimonials
October 16, 1677 Wrote Letter L-059 of 1677-10-16 to William Brouncker; he is sending some observations and a Latin translation
October 25, 1677 The Royal Society requested that Robert Hooke try to replicate Leeuwenhoek's observations
November 9, 1677 Wrote Letter L-060 of 1677-11-09 to William Brouncker about sperm and their movements in fresh human semen
November 11, 1677 Robert Hooke failed to demonstrate "minute animals" in pump water. The Royal Society read the testimonials from people in Delft.
November 15, 1677 Bought land near Berkelse Meer
November 18, 1677 Robert Hooke again failed, using an improved microscope
November 25, 1677 Robert Hooke finally succeeded in replicating Leeuwenhoek's observations of little animals
December 2, 1677 Wrote Letter L-061 of 1677-12-02 to William Brouncker; now lost
December 8, 1677 Constantijn Huygens wrote Letter L-062 to Leeuwenhoek about his observations of sperm
December 10, 1677 Robert Hooke wrote Letter L-063 to Leeuwenhoek to acknowledge the receipt of Letter L-060 of November 1677 to describing sperm in human semen
December 16, 1677 Robert Hooke demonstrated the superiority of single-lens over double-lens microscopes
January 1, 1678 Robert Hooke's Lectures and Collections: Cometa, Microscopium published
January 1, 1678 Wrote Letter L-064 of some time in 1678 to Robert Boyle; now lost
January 11, 1678 Nehemiah Grew and Robert Hooke wrote Letter L-065 to Leeuwenhoek asking him to further observe sperm
January 11, 1678 Nehemiah Grew wrote Letter L-066 of 1678-01-11 to Leeuwenhoek about comparisons of the size and shape of sperm from a variety of animals, the role of sperm in reproduction, and vessels in semen
January 14, 1678 Wrote Letter L-067 of 1678-01-14 to Robert Hooke about human blood, blood transfusions, flea larvae, and little animals in pepper water
January 27, 1678 Robert Hooke read Letter L-067 of 1678-01-14 at a meeting of the Royal Society
February 1, 1678 Empowered a Gouda notary to sell Vermeer's property to help pay Catherine Bolnes's creditors
February 3, 1678 Robert Hooke produced two experiments on blood and milk and read the latter part of the Letter L-067 of 1678-01-14 about phlegm and little animals in pepper water
February 11, 1678 Robert Hooke wrote Letter L-068 to Leeuwenhoek about how he verified Leeuwenhoek’s observations of little animals in a pepper infusion
February 14, 1678 Wrote Letter L-069 to Joseph Williamson, as Grew had requested
February 28, 1678 Christiaan Huygens began a series of observations of little animals replicating and expanding on Leeuwenhoek's
March 14, 1678 Christiaan Huygens observed little animals using dark-ground illumination
March 17, 1678 Robert Hooke showed the Royal Society microscopical observations of tendons and little animals in anise and coffee
March 18, 1678 Wrote Letter L-070 of 1678-03-18 to Nehemiah Grew about sperm in other animals and what Harvey and de Graaf got wrong about reproduction
March 24, 1678 Robert Hooke read his paper about his microscopic observations and methods
April 7, 1678 Robert Hooke showed the Royal Society microscopical observations of muscle from a lobster's claw
April 20, 1678 Nehemiah Grew wrote Letter L-071 of 1678-04-20 to Leeuwenhoek about his criticisms of Leeuwenhoek's work
April 28, 1678 Johannes Swammerdam wrote to Melchisedec Thévenot, saying that Leeuwenhoek "is biased, and reasons in a very barbarical way"
April 28, 1678 Robert Hooke wrote Letter L-072 to Leeuwenhoek that King Charles saw the little animals in pepper water
May 5, 1678 Robert Hooke showed the Royal Society microscopical observations of the motion and composition of muscles
May 9, 1678 niece Maria Jans de Molijn buried
May 31, 1678 Wrote Letter L-073 of 1678-05-31 to Nehemiah Grew about teeth, bone, hair, and sperm and what de Graaf got wrong about ovulation
June 6, 1678 Christiaan Huygens wrote to Nehemiah Grew about seeing the sperm in human semen
June 11, 1678 Christiaan Huygens observed little animals in water that Leeuwenhoek had sent to him
July 4, 1678 Lambert Twent named first postmaster of Delft
September 17, 1678 Christiaan Huygens again observed little animals using dark-ground illumination
September 27, 1678 Wrote Letter L-074 of 1678-09-27 to Nehemiah Grew about sweat and globules in saliva and blood
October 13, 1678 Nehemiah Grew wrote Letter L-075 of 1678-10-13 to Leeuwenhoek that Letter L-073 about male sperm and female ovulation in humans would be printed "as far as decency permits"
October 14, 1678 sister Margrieta Philips Leeuwenhoek buried
November 6, 1678 daughter Maria registered as a member of the Hervormde Gemeente Delft (Reformed Church in Delft)
November 10, 1678 Christiaan Huygens's method of melting powdered glass to make a spherical lens
December 23, 1678 Constantijn Huygens wrote Letter L-076 to Leeuwenhoek about the identification of little animals observed in pepper-water by his son Christiaan as well as the latter’s description of the scales on the wings of butterflies
December 26, 1678 Wrote Letter L-077 of 1678-12-26 to Constantijn Huygens about how son Christiaan's observations of little animals correspond to his own
January 25, 1679 Authorized to administer the estate of Ernst Gerrits de Bruijn
February 10, 1679 Appointed curator; Johannes Blaucamer guarantor
February 21, 1679 Wrote Letter L-078 of 1679-02-21 to Nehemiah Grew about cod sperm and about not finding any little animals in blood or saliva
April 1, 1679 cousin Maerten Huijchs Leeuwenhoek appointed tax master
April 12, 1679 Lambert van Velthuysen wrote Letter L-079 to Leeuwenhoek about arteries and nerves
April 25, 1679 Wrote Letter L-080 of 1679-04-25 to Nehemiah Grew about living little animals in fish, hare, and dogs and his calculation that more than ten times as many living animals come from the milt of a cod as there are people living on the Earth
April 27, 1679 Wrote Letter L-081 of 1679-04-27 to Constantijn Huygens about the number of sperm in the milt of the cod
May 1, 1679 Visited by James, Duke of York, and "several high personages"
May 4, 1679 Constantijn Huygens wrote Letter L-082 to Leeuwenhoek that his son Christiaan’s new book Dioptrica is about to be published
May 4, 1679 mentor Constantijn Huygens, writing to his son Christiaan, called Leeuwenhoek the "bourgeois philosopher of Delft"
May 11, 1679 Wrote Letter L-083 of 1679-05-11 to Lambert van Velthuysen about people with gout
May 15, 1679 Wrote Letter L-084 of 1679-05-15 to Christiaan Huygens to explain more about his observations of little animals
May 20, 1679 Wrote Letter L-085 of 1679-05-20 to Constantijn Huygens about the number and size of the little animals he was observing
June 1, 1679 Lambert van Velthuysen wrote Letter L-086 to Leeuwenhoek about the chalky discharges from gouty skin and his well-known controversy with the conservative supporters of the House of Orange
June 13, 1679 Wrote Letter L-087 of 1679-06-13 to Nehemiah Grew asking him to acknowledge two letters from earlier that year
June 13, 1679 Wrote Letter L-088 of 1679-06-13 to Lambert van Velthuysen about the origin of life and the lack of appreciation by physicians and surgeons
June 17, 1679 Lambert van Velthuysen wrote Letter L-089 to Leeuwenhoek about procreation
July 11, 1679 Wrote Letter L-090 of 1679-07-11 to Lambert van Velthuysen about about the chalk produced by gouty patients and about bladder stones
July 20, 1679 Robert Hooke read his translation of Letter L-080 of 1679-04-25 at a weekly meeting of the Royal Society
July 27, 1679 Robert Hooke showed the Royal Society microscopical observations of the liquor in a lamb's testicles
August 1, 1679 Robert Hooke wrote Letter L-091 of some time in August 1679 to Leeuwenhoek; now lost
August 10, 1679 Robert Hooke showed the Royal Society microscopical observations of a cock's testicles
August 15, 1679 Appointed city inspector of imported and exported liquids / wine gauger
August 25, 1679 Called "an unlearned, but ingenious man" by Peter Pels
September 4, 1679 colleague Nicolaas van der Sloot appointed co-wine gauger
September 17, 1679 Paid tax on his personal stock of wine
October 13, 1679 Wrote Letter L-092 of 1679-10-13 to Robert Hooke to inquire of Hooke why he had not received any correspondence from the Royal Society for months, also discussed bladder stones
October 18, 1679 Lambert van Velthuysen wrote Letter L-093 of 1679-10-18 to Leeuwenhoek about his delay in responding and gout
October 27, 1679 Robert Hooke wrote Letter L-094 of 1679-10-27 to Leeuwenhoek about examining fecund and sterile eggs for spots
October 30, 1679 cousin Pieter Abrahams Hogenhouck buried
November 1, 1679 Philosophical Collections number 1 published in London, including Leeuwenhoek's Letter 28 of 1679-04-25 (AB 43) to Nehemiah Grew
November 14, 1679 Wrote Letter L-095 of 1679-11-14 to Lambert van Velthuysen about gout, salt, and drinking tea
November 20, 1679 Wrote Letter L-096 of 1679-11-20 to Robert Hooke, copying his Letter L-095 of 14 November 1679 about gout, salt, and drinking tea
January 12, 1680 Wrote Letter L-097 of 1680-01-12 to Robert Hooke about the structure of wood and sperm in fish
January 16, 1680 Wrote Letter L-098 of 1680-01-16 to Robert Hooke, enclosing a copy of Letter L-085 of 1679-05-20 to Constantijn Huygens about the number and size of little animals
January 25, 1680 Robert Hooke read part of Letter L-096 of 1680-01-12 about the structure of wood
February 1, 1680 Robert Hooke read Letter L-085 to Huygens of 1679-05-20 about the number and size of little animals in ginger water
February 2, 1680 Robert Hooke wrote Letter L-099 to inquire whether Leeuwenhoek would accept election to the Royal Society
February 7, 1680 microscopist Jan Swammerdam died
February 8, 1680 Elected a member by the Royal Society
February 13, 1680 Wrote Letter L-100 of 1680-02-13 to Robert Hooke that being elected a member of the Royal Society would be an honour
February 18, 1680 cousin Margaretha (Grietjen) Huijchs Leeuwenhoek married Gijsbert Pieterse Cruijt
February 22, 1680 Thomas Gale authorized by the Royal Society to send diploma with seal to Leeuwenhoek
February 29, 1680 Royal Society ordered that its coat of arms be engraved on the silver box holding Leeuwenhoek's diploma
March 4, 1680 Royal Society discussed a silver box for Leeuwenhoek's diploma
March 7, 1680 Royal Society further discussed Leeuwenhoek's diploma
March 8, 1680 Thomas Gale wrote Letter L-101, sending Leeuwenhoek official notice of his election as member of the Royal Society
March 21, 1680 Royal Society postponed reading of Letter L-085 of 1679-05-20 to Huygens
March 28, 1680 Royal Society again postponed reading of Letter L-085 of 1679-05-20 to Huygens
April 5, 1680 Wrote Letter L-102 of 1680-04-05 to Robert Hooke about the testicles and sperm of a rat and organisms in the gills of oysters and in the sap of vines
April 11, 1680 Robert Hooke read Letter L-102 of 1680-04-05 about rat sperm and organisms in gills of oysters and sap of vines
April 22, 1680 Robert Hooke wrote Letter L-103 to Leeuwenhoek as official notice of his election as member of the Royal Society
May 13, 1680 Wrote Letter L-104 of 1680-05-13 to Members of the Royal Society expressing his surprise and gratitude at being elected a member
May 13, 1680 Wrote Letter L-105 of 1680-05-13 to Robert Hooke to gratefully accept his election as a foreign member of the Royal Society and to acknowledge the receipt of his diploma
May 13, 1680 Wrote Letter L-106 of 1680-05-13 to Thomas Gale about little animals in sap and whether little animals are in the air
May 23, 1680 Robert Hooke read the three letters of 1680-05-13 thanking the Royal Society

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