February 9 » The Davis Cup competition is established.
March 7 » The German liner SSKaiser Wilhelm der Grosse becomes the first ship to send wireless signals to shore.
June 14 » The second German Naval Law calls for the Imperial German Navy to be doubled in size, resulting in an Anglo-German naval arms race.
July 29 » In Italy, King Umberto I of Italy is assassinated by the anarchist Gaetano Bresci.
October 19 » Max Planck discovers Planck's law of black-body radiation.
November 7 » Second Boer War: Battle of Leliefontein, a battle during which the Royal Canadian Dragoons win three Victoria Crosses.
Day of marriage May 21, 1921
The temperature on May 21, 1921 was between 2.0 °C and 19.1 °C and averaged 12.6 °C. There was 12.7 hours of sunshine (80%). The average windspeed was 3 Bft (moderate breeze) and was prevailing from the north-northeast. 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.
January 16 » The Marxist Left in Slovakia and the Transcarpathian Ukraine holds its founding congress in Ľubochňa.
January 20 » The British K-class submarine HMS K5 sinks in the English Channel; all 56 on board die.
February 21 » Constituent Assembly of the Democratic Republic of Georgia adopts the country's first constitution.
February 21 » Rezā Shāh takes control of Tehran during a successful coup.
July 11 » Former president of the United States William Howard Taft is sworn in as 10th chief justice of the U.S. Supreme Court, becoming the only person ever to hold both offices.
July 23 » The Communist Party of China (CPC) is established at the founding National Congress.
When copying data from this family tree, please include a reference to the origin: Hans Weening, "Family tree Weening", database, Genealogy Online (https://www.genealogieonline.nl/stamboom-weening/I212360.php : accessed October 18, 2026), "Derktje Ronda (1900-)".
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