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.
July 2 » British-Italian engineer Guglielmo Marconi obtains a patent for radio in London.
August 21 » Oldsmobile, an American automobile manufacturer and marque, is founded.
September 11 » After months of pursuit, generals of Menelik II of Ethiopia capture Gaki Sherocho, the last king of Kaffa, bringing an end to that ancient kingdom.
December 30 » The British Colony of Natal annexes Zululand.
Day of marriage June 21, 1917
The temperature on June 21, 1917 was between 13.1 °C and 20.1 °C and averaged 16.5 °C. There was 5.8 mm of rain. There was 6.6 hours of sunshine (39%). The average windspeed was 3 Bft (moderate breeze) and was prevailing from the southwest. Source: KNMI
In The Netherlands , there was from August 29, 1913 to September 9, 1918 the cabinet Cort van der Linden, with Mr. P.W.A. Cort van der Linden (liberaal) as prime minister.
February 5 » The current constitution of Mexico is adopted, establishing a federal republic with powers separated into independent executive, legislative, and judicial branches.
March 1 » The Zimmermann Telegram is reprinted in newspapers across the United States after the U.S. government releases its unencrypted text.
April 12 » World War I: Canadian forces successfully complete the taking of Vimy Ridge from the Germans.
July 25 » Sir Robert Borden introduces the first income tax in Canada as a "temporary" measure (lowest bracket is 4% and highest is 25%).
October 13 » The "Miracle of the Sun" is witnessed by an estimated 70,000 people in the Cova da Iria in Portugal.
October 24 » First World War: Italy suffers a disastrous defeat on the Austro-Italian front.
When copying data from this family tree, please include a reference to the origin: Jan Kaper, "Family tree Kaper", database, Genealogy Online (https://www.genealogieonline.nl/stamboom-kaper/I14079.php : accessed March 6, 2026), "Aaltje Meinderdiena van Kampen (1897-????)".
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