| 38551 | April 4 | Event | 1969 – Dr. Denton Cooley implants the first temporary artificial heart. |
| 38552 | April 4 | Event | 1973 – The World Trade Center in New York is officially dedicated. |
| 38553 | April 4 | Event | 1973 – A Lockheed C-141 Starlifter, dubbed the Hanoi Taxi, makes the last flight of Operation Homecoming. |
| 38554 | April 4 | Event | 1975 – Microsoft is founded as a partnership between Bill Gates and Paul Allen in Albuquerque, New Mexico |
| 38555 | April 4 | Event | 1975 – Vietnam War: Operation Babylift: A United States Air Force Lockheed C-5A Galaxy transporting orphans, crashes near Saigon, South Vietnam shortly after takeoff killing 172 people. |
| 38556 | April 4 | Event | 1976 – Prince Norodom Sihanouk resigns as leader of Cambodia and is placed under house arrest. |
| 38557 | April 4 | Event | 1979 – Prime Minister Zulfikar Ali Bhutto of Pakistan is executed. |
| 38558 | April 4 | Event | 1981 – The Islamic Republic of Iran Air Force mounts an attack on H-3 Airbase and destroys about 50 Iraqi aircraft. |
| 38559 | April 4 | Event | 1983 – Space Shuttle Challenger makes its maiden voyage into space. |
| 38560 | April 4 | Event | 1984 – President Ronald Reagan calls for an international ban on chemical weapons. |
| 38561 | April 4 | Event | 1988 – Governor Evan Mecham of Arizona is convicted in his impeachment trial and removed from office. |
| 38562 | April 4 | Event | 1991 – Senator John Heinz of Pennsylvania and six others are killed when a helicopter collides with their airplane over an elementary school in Merion, Pennsylvania. |
| 38563 | April 4 | Event | 1991 – The current flag of Hong Kong is adopted for post-colonial Hong Kong during the Third Session of the Seventh National People's Congress. |
| 38564 | April 4 | Event | 1994 – Marc Andreessen and Jim Clark found Netscape Communications Corporation under the name Mosaic Communications Corporation. |
| 38565 | April 4 | Event | 1996 – Comet Hyakutake is imaged by the USA Asteroid Orbiter Near Earth Asteroid Rendezvous. |
| 38566 | April 4 | Event | 2002 – The Angolan government and UNITA rebels sign a peace treaty ending the Angolan Civil War. |
| 38567 | April 4 | Event | 2007 – Fifteen British Royal Navy personnel held in Iran are released by the Iranian President. |
| 38568 | April 4 | Event | 2009 – Three police officers are shot and killed during a shootout in Pittsburgh, Pennsylvania. |
| 38569 | April 4 | Event | 2013 – More than 70 people are killed in a building collapse in Thane, India. |
| 38570 | April 4 | Birth | 188 – Caracalla, Roman emperor (d. 217) |
| 38571 | April 4 | Birth | 1492 – Ambrosius Blarer, German-Swiss theologian and reformer (d. 1564) |
| 38572 | April 4 | Birth | 1572 – William Strachey, English author (d. 1621) |
| 38573 | April 4 | Birth | 1593 – Edward Nicholas, English soldier and politician, Secretary of State for the Southern Department (d. 1669) |
| 38574 | April 4 | Birth | 1640 – Gaspar Sanz, Spanish guitarist, composer, and priest (d. 1710) |
| 38575 | April 4 | Birth | 1646 – Antoine Galland, French orientalist and archaeologist (d. 1715) |
| 38576 | April 4 | Birth | 1648 – Grinling Gibbons, Dutch-English sculptor (d. 1721) |
| 38577 | April 4 | Birth | 1676 – Giuseppe Maria Orlandini, Italian composer (d. 1760) |
| 38578 | April 4 | Birth | 1688 – Joseph-Nicolas Delisle, French astronomer and cartographer (d. 1768) |
| 38579 | April 4 | Birth | 1718 – Benjamin Kennicott, English theologian and scholar (d. 1783) |
| 38580 | April 4 | Birth | 1752 – Niccolò Antonio Zingarelli, Italian composer (d. 1837) |