April 18 » The Greco-Turkish War is declared between Greece and the Ottoman Empire.
June 16 » A treaty annexing the Republic of Hawaii to the United States is signed; the Republic would not be dissolved until a year later.
August 10 » German chemist Felix Hoffmann discovers an improved way of synthesizing acetylsalicylic acid (aspirin).
August 21 » Oldsmobile, an American automobile manufacturer and marque, is founded.
August 31 » Thomas Edison patents the Kinetoscope, the first movie projector.
September 1 » The Tremont Street Subway in Boston opens, becoming the first underground rapid transit system in North America.
Day of marriage December 31, 1921
The temperature on December 31, 1921 was between 3.4 °C and 7.7 °C and averaged 5.4 °C. There was 2.9 mm of rain. There was 0.4 hours of sunshine (5%). The average windspeed was 5 Bft (very strong wind) and was prevailing from the west-northwest. Source: KNMI
In The Netherlands , there was from September 9, 1918 to September 18, 1922 the cabinet Ruys de Beerenbrouck I, with Jonkheer mr. Ch.J.M. Ruys de Beerenbrouck (RKSP) as prime minister.
May 31 » The Tulsa race massacre kills at least 39, but other estimates of black fatalities vary from 55 to about 300.
July 2 » World War I: U.S. President Warren G. Harding signs the Knox–Porter Resolution formally ending the war between the United States and Germany.
July 23 » The Communist Party of China (CPC) is established at the founding National Congress.
September 5 » Roscoe "Fatty" Arbuckle party in San Francisco ends with the death of the young actress Virginia Rappe: One of the first scandals of the Hollywood community.
September 11 » Nahalal, the first moshav in Palestine, is settled as part of a Zionist plan of creating a Jewish state, later to be Israel.
October 19 » The Portuguese Prime Minister and several officials are murdered in the Bloody Night coup.
When copying data from this family tree, please include a reference to the origin: Tjitze Koster, "Family tree Koster Twijslerheide e.o.", database, Genealogy Online (https://www.genealogieonline.nl/stamboom-koster/I3104.php : accessed February 15, 2026), "Pieter Koster (1897-????)".
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