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
January 1, 1663 Christiaen Anhaltin's School-Boeck van de Wyn-Royeryen published
January 25, 1663 son Philips Leeuwenhoek (second) baptized, buried three weeks later
April 25, 1663 brother-in-law Adriaan Johannes Swalmius (1631-1667) married Margrieta van der Burch
July 2, 1663 Christiaan Huygens elected member of the Royal Society
August 1, 1663 Christiaan Huygens received letter from Gutschoven about how to grind small lenses
January 1, 1664 cousin Maerten Huijchs Leeuwenhoek appointed tax farmer
February 19, 1664 cousin Sara Maertens Leeuwenhoek (1664-1693) baptized
May 11, 1664 nephew Johannes Adriaans Swalmius (1664-1693) baptized
June 25, 1664 Bought a garden outside the walls of the city
August 19, 1664 son Philips Leeuwenhoek (third) baptized
September 3, 1664 mother Margriete Jacobs van den Berch (1594-1664) buried in Oude Kerk
September 29, 1664 Owed for store goods by the estate of Elizabeth Cornelis
November 25, 1664 Received a legacy from the estate of great-aunt Aaltge Sebastiaans van den Berch
January 1, 1665 Robert Hooke's Micrographia published
March 26, 1665 Christiaan Huygens acquired Hooke's Micrographia
July 31, 1665 Appointed guardian of second cousin Maria van Halmael
January 1, 1666 mentor Reinier de Graaf (1641-1673) moved to Delft
May 28, 1666 cousin Elisabeth Maertens Leeuwenhoek (1666-1743) baptized
June 27, 1666 son Philips Leeuwenhoek (third) buried in Oude Kerk
July 14, 1666 wife Barbara de Meij buried in Oude Kerk
October 10, 1666 Appointed district supervisor (wijkmeester generaal)
January 1, 1667 Dirck van Bleyswyck's Beschryvinge der Stadt Delft, Description of the City of Delft, published
February 5, 1667 mentor Jacob Spoors married Trijntge Jans
March 11, 1667 Presented will after wife Barbara's death
May 2, 1667 brother-in-law Adriaan Johannes Swalmius (1631-1667) buried
May 18, 1667 Appointed curator of estate of Simon de Bourbon
July 15, 1667 Appeared before the Weescamer to begin the process of curating the estate of Simon de Bourbon
September 15, 1667 aunt Cornelia Jacobs van den Berch buried in Oude Kerk
January 1, 1668 Conducted an experiment with grapevines
January 1, 1668 Traveled to England
June 13, 1668 grandfather Thonis Phillips Leeuwenhoek's will of 1643 presented
November 14, 1668 Delivered to the Weescamer his first accounting as curator over the person and assets of Sijmon Bourbon
January 1, 1669 cousin Pieter Abrahams Hogenhouck (-1679) appointed mayor in 1669-1673, 1677
February 4, 1669 Certified as a surveyor after passing the oral examination
February 15, 1669 uncle Huijch Thonis Leeuwenhoek buried in Nieuwe Kerk
October 8, 1669 daughter Maria named in will of her aunt Maria de Meij
July 13, 1670 cousin Cornelis Lambrechts Leeuwenhoek (1670-1702) baptized
August 30, 1670 Signed a will as clerk and witness for notary Joris van der Houve
September 2, 1670 Appointed co-wine gauger to help Dirk Arisz.
November 28, 1670 Delivered to the Weescamer his second accounting as curator over the person and assets of Sijmon Bourbon
December 2, 1670 Signed a will as clerk and witness for notary Paul Durven
December 16, 1670 Delivered to the Weescamer the document disposing of the late Sijmon Bourbon's assets
January 8, 1671 Testified to marriage conditions with Cornelia Swalmius
January 17, 1671 daughter Maria made a will
January 25, 1671 Married Cornelia Johannes Swalmius
April 14, 1671 Agreed to act as steward for land inherited by second wife Cornelia
April 15, 1671 Signed a will as clerk and witness for notary Paul Durven
May 30, 1671 cousin Anthonij Lambrechts Leeuwenhoek (1653-1671) buried in Oude Kerk
October 15, 1671 wife Cornelia Johannes Swalmius made a will
January 10, 1672 sister-in-law Elisabeth Johannes Swalmius married Paulus Marcel
February 17, 1672 Jan Strick was buried
April 9, 1672 Disaster Year: Delft sent troops to help defend against the invading French army
June 12, 1672 mentor Reinier de Graaf married Maria van Dijck
June 29, 1672 Disaster Year: unemployed protestors from Schiedam occupied Delft city hall
July 8, 1672 Prince Willem III wrote to the burgemeesters of Delft that those not cooperating in repelling the enemy will be severely punished
September 10, 1672 Prince Willem III wrote to the burgemeesters of Delft concerning the naming of new regents
September 10, 1672 Disaster Year: half of the Veertigraad replaced with pro-Orangist regents
September 10, 1672 mentor Dr. Cornelis 's Gravesande appointed to Veertigraad
September 21, 1672 daughter Maria made a will
November 7, 1672 nephew Arnold Marcel (1672-1748) baptized in Dordrecht
April 1, 1673 cousin Magdaleentje (Helena) Maertens Leeuwenhoek (1653-1720) married Johannes de Coep
April 28, 1673 Wrote Letter L-001 of 1673-04-28 to Henry Oldenburg about mould and a bee's stinger and eye
May 17, 1673 The Royal Society received Leeuwenhoek's first letter
May 19, 1673 At age 40, first letter published in Philosophical Transactions
May 25, 1673 Henry Oldenburg wrote to Reinier de Graaf about the Royal Society's reception of Leeuwenhoek's first letter
August 8, 1673 mentor Constantijn Huygens wrote to Robert Hooke about Leeuwenhoek as "exceedingly curious and industrious"
August 15, 1673 Wrote Letter L-002 of 1673-08-15 to Henry Oldenburg about the bee, the movement of liquids in wood and food in a louse, and the composition of air
August 21, 1673 mentor Reinier de Graaf buried
October 16, 1673 First letter's ten figures published in Philosophical Transactions
October 24, 1673 Leeuwenhoek's family members in 1673
November 8, 1673 Wrote Letter L-003 of 1673-11-08 to Henry Oldenburg about globules in milk and in blood and his theory on the structure and growth of hair and of tumours
November 28, 1673 Named as administrator of the estate of Willem Jans Croonenburgh
January 1, 1674 Paid the Familiegeld (estate tax)
February 1, 1674 Constantijn Huygens wrote Letter L-004 to Leeuwenhoek, enclosing an extract of a letter from Oldenburg that asked Huygens to encourage L.’s nature study
February 12, 1674 Constantijn Huygens wrote to Oldenburg about Leeuwenhoek and his own single-lens microscope
March 10, 1674 nieces Margrieta and Maria Jans de Molijn married Arnoldus van den Heuvel and Cornelis Haaxman
March 18, 1674 sister-in-law Maria de Meij married Pieter Schepens
April 5, 1674 Wrote Letter L-005 of 1674-04-05 to Constantijn Huygens about globules in milk and blood and the growth of hair; first mention of red blood corpuscles
April 7, 1674 Wrote Letter L-006 of 1674-04-07 to Henry Oldenburg about globules in milk and blood, the growth of hair and nails, and the anatomy of a louse
April 11, 1674 Constantijn Huygens wrote Letter L-007 to Leeuwenhoek about sending his observations to son Christiaan in Paris
April 16, 1674 Wrote Letter L-008 of 1674-04-16 to Henry Oldenburg about the delivery of his letters and asking Oldenburg to befriend van Conincxbrugh
April 24, 1674 Appointed curator of the abandoned estate of Bartholomeus Ritmeier
April 24, 1674 Wrote Letter L-009 of 1674-04-24 to Constantijn Huygens about his further observations about blood, bones, teeth, and salt
May 4, 1674 Henry Oldenburg wrote Letter L-010 to Leeuwenhoek requesting that he examine saliva, chyle, and sweat
June 1, 1674 Wrote Letter L-011 of 1674-06-01 to Henry Oldenburg about movement of liquid in capillary tubes, structure of body parts, growth of skin, and the size of red blood cells
July 6, 1674 Wrote Letter L-012 of 1674-07-06 to Henry Oldenburg bout sweat, hair, fat, tears, and improved capillary tubes
August 1, 1674 First observed little animals in water
August 11, 1674 Visited by Holger Jacobæus, the Bartholin brothers, and Arent Seyn; described as "ingenious but illiterate"
August 15, 1674 Visited by Johannes Swammerdam
August 16, 1674 Ordered as curator to hand over the debt books of Bartholomeus Ritmeier
August 24, 1674 daughter Maria made a will
August 30, 1674 Henry Oldenburg wrote Letter L-013 to Leeuwenhoek, encouraging him to send more observations
September 7, 1674 Wrote Letter L-014 of 1674-09-07 to Henry Oldenburg, stating that he will send further observations
September 7, 1674 Wrote Letter L-015 of 1674-09-07 to Henry Oldenburg about the anatomy of the eye and optic nerve of a cow, minerals eg. salt, clay, English and Flemish earth; first mention of protozoa in stagnant water
October 19, 1674 Wrote Letter L-016 of 1674-10-19 to Henry Oldenburg about eggs in the bile of cow, sheep, rabbits and poultry, the structure of metals, skin, and the bladder, and theories about the sense of taste.
October 25, 1674 The Royal Society began requiring an oath of secrecy from the members who attended meetings
November 5, 1674 Henry Oldenburg wrote Letter L-017 to Leeuwenhoek encouraging him and asking about the kind of salt he was observing
November 22, 1674 The Royal Society asked Olderburg to produce Leeuwenhoek's Letter L-011 of 1 June 1674
December 4, 1674 Wrote Letter L-018 of 1674-12-04 to Henry Oldenburg about optic nerves and sight; enclosed specimen of cow's optic nerve
December 21, 1674 Appointed to administer the affairs of sister-in-law Maria de Meij
December 22, 1674 sister-in-law Maria de Meij and Pieter Schepens granted a divorce
December 26, 1674 Wrote Letter L-019 of 1674-12-26 to Constantijn Huygens, enclosing a drawing of the optic nerve and excerpts from two recent letters
December 31, 1674 sister-in-law Catharina Swalmius buried
January 1, 1675 cousin Maerten Huijchs Leeuwenhoek appointed tax farmer
January 3, 1675 Henry Oldenburg wrote Letter L-020 to Leeuwenhoek about his doubts about globules
January 20, 1675 Christiaan Huygens wrote to Henry Oldenburg doubting Leeuwenhoek's observations of globules
January 22, 1675 Wrote Letter L-021 of 1675-01-22 to Henry Oldenburg about a new technique for observing blood and sectioned brain tissue; optic nerve, smoke, gunpowder, and scorpions
February 11, 1675 Wrote Letter L-022 of 1675-02-11 to Henry Oldenburg about crystals, vinegar, soap, spices, cod, louse, and oak leaf.
February 12, 1675 Henry Oldenburg wrote to Christiaan Huygens about doubting Leeuwenhoek's globules
March 1, 1675 Henry Oldenburg wrote Letter L-023 to Leeuwenhoek in response to his Letter L-021 of 1675-01-22
March 26, 1675 Wrote Letter L-024 of 1675-03-26 to Henry Oldenburg about meals, seeds, and pearls; transparency; movement of fluids in plants and animals
April 22, 1675 Henry Oldenburg wrote Letter L-025 to Leeuwenhoek recommending that he get help from knowledgable people
August 14, 1675 Wrote Letter L-026 of 1675-08-14 to Henry Oldenburg about blood, taste of saps, sugar, and salt, and the mechanics of taste and digestion
August 22, 1675 Henry Oldenburg wrote Letter L-027 to Leeuwenhoek acknowledging reciept of his letters
September 15, 1675 First observed little animals in rain water
September 20, 1675 Appointed curator of estate of Henricus van Zuijlen
December 15, 1675 Jan Vermeer, the painter, buried
December 20, 1675 Wrote Letter L-028 of 1675-12-20 to Henry Oldenburg about various omissions in previous letters, small animals in water, his theory of “globules”, and the aerometer he devised
January 1, 1676 Wrote Letter L-029 of some time in 1676 to Theodore Craanen about gold and mercury
January 7, 1676 Henry Oldenburg wrote Letter L-030 to Leeuwenhoek about the reaction in London to his observations
January 22, 1676 Wrote Letter L-031 of 1676-01-22 to Henry Oldenburg about forwarding his mail and about sending his observations of little animals in water
January 26, 1676 sister-in-law Maria de Meij buried
February 13, 1676 Henry Oldenburg wrote Letter L-032 to Leeuwenhoek requesting that he examine hair
February 20, 1676 Henry Oldenburg wrote Letter L-033 to Leeuwenhoek and pre-paid the postage
February 22, 1676 Wrote Letter L-034 of 1676-02-22 to Henry Oldenburg about hair, cow skin, horn, and bone, inviting Hooke's response
April 5, 1676 co-worker Daniel Bogaert married Maria van Rees
April 21, 1676 Wrote Letter L-035 of 1676-04-21 to Henry Oldenburg about movement of liquid in ash and other trees, little animals in wine, and cinnamon and taste
April 24, 1676 Began series of experiments to observe little animals in spice infusions
April 26, 1676 Began Pepper 2 experiment
May 1, 1676 Constantijn Huygens wrote to Oldenburg that Leeuwenhoek gave him an issue of Philosophical Transactions
May 14, 1676 Henry Oldenburg wrote Letter L-036 to Leeuwenhoek about Hooke's and Grew's reactions to recent observations
May 29, 1676 Wrote Letter L-037 of 1676-05-29 to Henry Oldenburg about disagreements with Grew about the structure of wood and a further account of the vessels, fibres, and medullary rays of wood
July 1, 1676 Visited by Christiaan Huygens during the summer; he saw the little animals in Leeuwenhoek's infusions
July 28, 1676 Wrote Letter L-038 of 1676-07-28 to Henry Oldenburg; now lost
July 28, 1676 Wrote Letter L-039 of 1676-07-28 to Robert Boyle about the effects of air on ammonia and copper
September 30, 1676 Appointed curator of estate of Catherine Bolnes, Vermeer's widow
October 9, 1676 Wrote Letter L-040 of 1676-10-09 to Henry Oldenburg about little animals in various waters and spice infusions, the relationship of their shape to taste, and whether there were little animals in the air
October 18, 1676 Henry Oldenburg wrote Letter L-041 to Leeuwenhoek; sent Philosophical Transactions no. 127
October 23, 1676 mentor Cornelis 's Gravesande lent money to Sijmons Decker
October 26, 1676 Henry Oldenburg wrote Letter L-042 to Leeuwenhoek acknowledging receipt of the letter of 1676-10-09

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