- 1862 The first pasteurization test is completed by Frenchmen Louis Pasteur and Claude Bernard.
- 1902 Marie & Pierre Curie isolate the radioactive element radium chloride
- 1920 Balfour Declaration recognized, makes Palestine a British Mandate
- 1968 English politician Enoch Powell makes his controversial "Rivers of Blood" speech.
- 1974 'The Troubles', the Northern Ireland conflict between republican and loyalist paramilitaries, British security forces, and civil rights groups, claims its 1000th victim
- 1980 Climax of Berber Spring in Algeria as hundreds of Berber political activists are arrested.
- 1999 Columbine High School massacre: Eric Harris and Dylan Klebold kill 13 people and injure 24 others before committing suicide at Columbine High School, Colorado
Frenchman René Caillié is the first non-Muslim to enter Timbuktu, returns to win 10,000 franc prize from Société de Géographie
On April 20, 1828