| 45539 | April 20 | Birth | 1808 – Napoleon III, French politician, 1st President of France (d. 1873) |
| 45540 | April 20 | Birth | 1816 – Bogoslav Šulek, Croatian philologist, historian, and lexicographer (d. 1895) |
| 45511 | April 20 | Event | 1961 – Failure of the Bay of Pigs Invasion of US-backed Cuban exiles against Cuba. |
| 45512 | April 20 | Event | 1964 – BBC Two launches with a power cut because of the fire at Battersea Power Station. |
| 45513 | April 20 | Event | 1968 – English politician Enoch Powell makes his controversial Rivers of Blood speech. |
| 45514 | April 20 | Event | 1972 – Apollo 16, commanded by John Young, lands on the moon. |
| 45515 | April 20 | Event | 1978 – Korean Air Lines Flight 902 is shot down by the Soviet Union. |
| 45516 | April 20 | Event | 1980 – Climax of Berber Spring in Algeria as hundreds of Berber political activists are arrested. |
| 45517 | April 20 | Event | 1984 – The Good Friday Massacre, an extremely violent ice hockey playoff game, is played in Montreal, Canada. |
| 45518 | April 20 | Event | 1985 – The ATF raids The Covenant, The Sword, and the Arm of the Lord compound in northern Arkansas. |
| 45519 | April 20 | Event | 1986 – Pianist Vladimir Horowitz performs in his native Russia for the first time in 61 years. |
| 45520 | April 20 | Event | 1998 – German terrorist group the Red Army Faction announces their dissolution after 28 years. |
| 45521 | April 20 | Event | 1999 – Columbine High School massacre: Eric Harris and Dylan Klebold killed 13 people and injured 21 others before committing suicide at Columbine High School in Columbine, Colorado. |
| 45522 | April 20 | Event | 2007 – Johnson Space Center shooting: William Phillips with a handgun barricades himself in NASA's Johnson Space Center in Houston, Texas before killing a male hostage and himself. |
| 45523 | April 20 | Event | 2008 – Danica Patrick wins the Indy Japan 300 becoming the first female driver in history to win an Indy car race. |
| 45524 | April 20 | Event | 2010 – The Deepwater Horizon drilling rig explodes in the Gulf of Mexico, killing eleven workers and beginning an oil spill that would last six months. |
| 45525 | April 20 | Event | 2012 – One hundred twenty-seven people are killed when a plane crashes in a residential area near the Benazir Bhutto International Airport near Islamabad, Pakistan. |
| 45526 | April 20 | Event | 2013 – A 6.6-magnitude earthquake strikes Lushan County, Ya'an, in China's Sichuan province, killing more than 150 people and injuring thousands. |
| 45527 | April 20 | Event | 2015 – 10 people are killed in a bomb attack on a convoy carrying food supplies to a United Nations compound in Garowe in the Somali region of Puntland. |
| 45528 | April 20 | Birth | 1492 – Pietro Aretino, Italian author, playwright, and poet (d. 1556) |
| 45529 | April 20 | Birth | 1494 – Johannes Agricola, German theologian and reformer (d. 1566) |
| 45530 | April 20 | Birth | 1586 – Rose of Lima, Peruvian mystic and saint (d. 1617) |
| 45531 | April 20 | Birth | 1633 – Emperor Go-Kōmyō of Japan (d. 1654) |
| 45532 | April 20 | Birth | 1646 – Charles Plumier, French botanist and author (d. 1704) |
| 45533 | April 20 | Birth | 1650 – William Bedloe, English spy (d. 1680) |
| 45534 | April 20 | Birth | 1718 – David Brainerd, American missionary (d. 1747) |
| 45535 | April 20 | Birth | 1723 – Cornelius Harnett, American merchant, farmer, and politician (d. 1781) |
| 45536 | April 20 | Birth | 1727 – Florimond Claude, Comte de Mercy-Argenteau, Belgian-Austrian minister and diplomat (d. 1794) |
| 45537 | April 20 | Birth | 1745 – Philippe Pinel, French physician and psychiatrist (d. 1826) |
| 45538 | April 20 | Birth | 1748 – Georg Michael Telemann, German composer and theologian (d. 1831) |