| 30991 | March 20 | Event | 1883 – The Paris Convention for the Protection of Industrial Property is signed. |
| 30992 | March 20 | Event | 1888 – The premiere of the very first Romani language operetta is staged in Moscow, Russia. |
| 30993 | March 20 | Event | 1913 – Sung Chiao-jen, a founder of the Chinese Nationalist Party, is wounded in an assassination attempt and dies 2 days later. |
| 30994 | March 20 | Event | 1916 – Albert Einstein publishes his general theory of relativity. |
| 30995 | March 20 | Event | 1922 – The USS Langley is commissioned as the first United States Navy aircraft carrier. |
| 30996 | March 20 | Event | 1923 – The Arts Club of Chicago hosts the opening of Pablo Picasso's first United States showing, entitled Original Drawings by Pablo Picasso, becoming an early proponent of modern art in the United States. |
| 30997 | March 20 | Event | 1933 – Giuseppe Zangara is executed in Florida's electric chair for fatally shooting Anton Cermak in an assassination attempt against President-Elect Franklin D. Roosevelt. |
| 30998 | March 20 | Event | 1933 – Reichsführer-SS Heinrich Himmler ordered the creation of Dachau concentration camp as Chief of Police of Munich and appointed Theodor Eicke as the camp commandant. |
| 30999 | March 20 | Event | 1942 – World War II: General Douglas MacArthur, at Terowie, South Australia, makes his famous speech regarding the fall of the Philippines, in which he says: "I came out of Bataan and I shall return". |
| 31000 | March 20 | Event | 1948 – With a Musicians Union ban lifted, the first telecasts of classical music in the United States, under Eugene Ormandy and Arturo Toscanini, are given on CBS and NBC. |
| 31001 | March 20 | Event | 1951 – Fujiyoshida, a city located in Yamanashi Prefecture, Japan, in the center of the Japanese main island of Honshū is founded. |
| 31002 | March 20 | Event | 1952 – The United States Senate ratifies a peace treaty with Japan. |
| 31003 | March 20 | Event | 1956 – Tunisia gains independence from France. |
| 31004 | March 20 | Event | 1964 – The precursor of the European Space Agency, ESRO (European Space Research Organisation) is established per an agreement signed on June 14, 1962. |
| 31005 | March 20 | Event | 1972 – The Troubles: The first Provisional IRA car bombing in Belfast kills seven people and injures 148 others in Northern Ireland. |
| 31006 | March 20 | Event | 1974 – An unsuccessful attempt is made by a lone perpetrator to kidnap Her Royal Highness Princess Anne and her husband Captain Mark Phillips in The Mall, outside Buckingham Palace, London. |
| 31007 | March 20 | Event | 1980 – The Radio Caroline ship, Mi Amigo founders in a gale off the English coast. |
| 31008 | March 20 | Event | 1985 – Libby Riddles becomes the first woman to win the 1,135-mile Iditarod Trail Sled Dog Race. |
| 31009 | March 20 | Event | 1985 – Canadian paraplegic athlete and humanitarian Rick Hansen begins his circumnavigation of the globe in a wheelchair in the name of spinal cord injury medical research. |
| 31010 | March 20 | Event | 1987 – The Food and Drug Administration approves the anti-AIDS drug, AZT. |
| 31011 | March 20 | Event | 1988 – Eritrean War of Independence: Having defeated the Nadew Command, the Eritrean People's Liberation Front enters the town of Afabet, victoriously concluding the Battle of Afabet. |
| 31012 | March 20 | Event | 1990 – Ferdinand Marcos's widow, Imelda Marcos, goes on trial for bribery, embezzlement, and racketeering. |
| 31013 | March 20 | Event | 1993 – The Troubles: A Provisional IRA bomb kills two children in Warrington, England. It leads to mass protests in both Britain and Ireland. |
| 31014 | March 20 | Event | 1995 – A sarin gas attack on the Tokyo subway kills 13 and wounds 1,300 people. |
| 31015 | March 20 | Event | 1999 – Legoland California, the first Legoland outside of Europe, opens in Carlsbad, California. |
| 31016 | March 20 | Event | 2000 – Jamil Abdullah Al-Amin, a former Black Panther once known as H. Rap Brown, is captured after murdering Georgia sheriff's deputy Ricky Kinchen and critically wounding Deputy Aldranon English. |
| 31017 | March 20 | Event | 2003 – Invasion of Iraq: In the early hours of the morning, the United States and three other countries (the UK, Australia and Poland) begin military operations in Iraq. |
| 31018 | March 20 | Event | 2006 – Over 150 Chadian soldiers are killed in eastern Chad by members of the rebel UFDC. The rebel movement sought to overthrow Chadian president Idriss Déby. |
| 31019 | March 20 | Event | 2012 – At least 52 people are killed and more than 250 injured in a wave of terror attacks across ten cities in Iraq. |
| 31020 | March 20 | Event | 2014 – Four suspected Taliban members attack the luxurious Kabul Serena Hotel, killing at least nine people. |