January 31 » Czechoslav Trade Union Association is founded in Prague.
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 22 » British colonial officers Charles Walter Rand and Lt. Charles Egerton Ayerst are assassinated in Pune, Maharashtra, India by the Chapekar brothers and Mahadeo Vinayak Ranade, who are later caught and hanged.
July 11 » Salomon August Andrée leaves Spitsbergen to attempt to reach the North Pole by balloon. He later crashes and dies.
July 26 » Anglo-Afghan War: The Pashtun fakir Saidullah leads an army of more than 10,000 to begin a siege of the British garrison in the Malakand Agency of the North West Frontier Province of India.
August 31 » Thomas Edison patents the Kinetoscope, the first movie projector.
Day of death May 25, 1921
The temperature on May 25, 1921 was between 10.8 °C and 29.0 °C and averaged 20.1 °C. There was 12.9 hours of sunshine (80%). The average windspeed was 3 Bft (moderate breeze) and was prevailing from the 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.
February 15 » Kingdom of Romania establishes its legation in Helsinki.
February 27 » The International Working Union of Socialist Parties is founded in Vienna.
March 1 » Following mass protests in Petrograd demanding greater freedom in the RSFSR, the Kronstadt rebellion began, with sailors and citizens taking up arms against the Bolsheviks.
May 8 » The creation of the Communist Party of Romania.
October 26 » The Chicago Theatre opens.
November 11 » The Tomb of the Unknowns is dedicated by US President Warren G. Harding at Arlington National Cemetery.
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/I132870.php : accessed October 21, 2026), "Johannes Piersma (1897-1921)".
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