April 18 » The Greco-Turkish War is declared between Greece and the Ottoman Empire.
April 30 » J. J. Thomson of the Cavendish Laboratory announces his discovery of the electron as a subatomic particle, over 1,800 times smaller than a proton (in the atomic nucleus), at a lecture at the Royal Institution in London.
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 31 » Thomas Edison patents the Kinetoscope, the first movie projector.
December 9 » Activist Marguerite Durand founds the feminist daily newspaper La Fronde in Paris.
Day of marriage April 20, 1921
The temperature on April 20, 1921 was between -1.6 °C and 10.4 °C and averaged 5.0 °C. There was 4.1 mm of rain. There was 4.9 hours of sunshine (35%). The average windspeed was 3 Bft (moderate breeze) 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.
February 25 » Georgian capital Tbilisi falls to the invading Russian forces after heavy fighting and the Russians declare the Georgian Soviet Socialist Republic.
March 19 » Irish War of Independence: One of the biggest engagements of the war takes place at Crossbarry, County Cork. About 100 Irish Republican Army (IRA) volunteers escape an attempt by over 1,300 British forces to encircle them.
June 20 » Workers of Buckingham and Carnatic Mills in the city of Chennai, India, begin a four-month strike.
July 22 » Rif War: The Spanish Army suffers its worst military defeat in modern times to the Berbers of the Rif region of Spanish Morocco.
August 14 » Tannu Uriankhai, later Tuvan People's Republic is established as a completely independent country (which is supported by Soviet Russia).
August 28 » The Red Army dissolved the Free Territory, after driving the Black Army out of Ukraine.
When copying data from this family tree, please include a reference to the origin: R.A.Hemerik, "Descendants Hemerik-Broekhuizen-Huner-Koper-Barink", database, Genealogy Online (https://www.genealogieonline.nl/parenteel-hemerik/I41507.php : accessed March 13, 2026), "Matthijs Kasteel (1897-????)".
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