2014: The American city of Flint, Michigan switches its water source to the Flint River, beginning the ongoing Flint water crisis which has caused lead poisoning in up to 12,000 people, and 15 deaths from Legionnaires disease, ultimately leading to criminal indictments against 15 people, five of whom have been charged with involuntary manslaughter.
2012: Two trains are involved in a head-on collision near Sloterdijk, Amsterdam, in the Netherlands, injuring 116 people.
2004: Five suicide car bombers target police stations in and around Basra, killing 74 people and wounding 160.
1993: The Supreme Court in La Paz, Bolivia, sentences former dictator Luis García Meza to 30 years in jail without parole for murder, theft, fraud and violating the constitution.
1992: The first discoveries of extrasolar planets are announced by astronomers Aleksander Wolszczan and Dale Frail. They discovered two planets orbiting the pulsar PSR 1257+12.
1967: Greek military junta of 1967-74: A few days before the general election in Greece, Colonel George Papadopoulos leads a coup d'état, establishing a military regime that lasts for seven years.
1965: The 1964-1965 New York World's Fair opens for its second and final season.
1964: A Transit-5bn satellite fails to reach orbit after launch; as it re-enters the atmosphere, 2.1 pounds (0.95 kg) of radioactive plutonium in its SNAP RTG power source is widely dispersed.
1960: Brasília, Brazil's capital, is officially inaugurated. At 09:30, the Three Powers of the Republic are simultaneously transferred from the old capital, Rio de Janeiro.
1952: Secretary's Day (now Administrative Professionals' Day) is first celebrated.
1945: World War II: Soviet forces south of Berlin at Zossen attack the German High Command headquarters.
1934: The "Surgeon's Photograph", the most famous photo allegedly showing the Loch Ness Monster, is published in the Daily Mail (in 1999, it is revealed to be a hoax).
1926: Al-Baqi cemetery, former site of the mausoleum of four Shi'a Imams, is leveled to the ground by Wahhabis.
1914: Ypiranga incident: A German arms shipment to Mexico is intercepted by the U.S. Navy near Veracruz.
1898: Spanish-American War: The United States Navy begins a blockade of Cuban ports. When the U.S. Congress issued a declaration of war on April 25, it declared that a state of war had existed from this date.
1894: Norway formally adopts the Krag-Jørgensen bolt-action rifle as the main arm of its armed forces, a weapon that would remain in service for almost 50 years.
1856: Australian labour movement: Stonemasons and building workers on building sites around Melbourne march from the University of Melbourne to Parliament House to achieve an eight-hour day.
1809: Two Austrian army corps are driven from Landshut by a First French Empire army led by Napoleon as two French corps to the north hold off the main Austrian army on the first day of the Battle of Eckmühl.
1806: Action of 21 April 1806: A French frigate escapes British forces off the coast of South Africa.
1792: Tiradentes, a revolutionary leading a movement for Brazil's independence, is hanged, drawn and quartered.
1782: The city of Rattanakosin, now known internationally as Bangkok, is founded on the eastern bank of the Chao Phraya River by King Buddha Yodfa Chulaloke.
900: The Laguna Copperplate Inscription (the earliest known written document found in what is now the Philippines): the Commander-in-Chief of the Kingdom of Tondo, as represented by the Honourable Jayadewa, Lord Minister of Pailah, pardons from all debt the Honourable Namwaran and his relations.