| 37171 | April 1 | Event | 1922 – Six Irish Catholic civilians are shot and beaten to death by a gang of policemen in Belfast, Northern Ireland. |
| 37172 | April 1 | Event | 1924 – Adolf Hitler is sentenced to five years in jail for his participation in the "Beer Hall Putsch". However, he spends only nine months in jail, during which he writes Mein Kampf. |
| 37173 | April 1 | Event | 1924 – The Royal Canadian Air Force is formed. |
| 37174 | April 1 | Event | 1933 – The recently elected Nazis under Julius Streicher organize a one-day boycott of all Jewish-owned businesses in Germany, ushering in a series of anti-Semitic acts. |
| 37175 | April 1 | Event | 1935 – India's central banking institution, The Reserve Bank of India is formed. |
| 37176 | April 1 | Event | 1936 – Odisha formerly known as Kalinga or Utkal becomes a state in India. |
| 37177 | April 1 | Event | 1937 – Aden becomes a British crown colony. |
| 37178 | April 1 | Event | 1937 – Spanish Civil War: Jaén, Spain is bombed by Nazi forces. |
| 37179 | April 1 | Event | 1939 – Spanish Civil War: Generalísimo Francisco Franco of the Spanish State announces the end of the Spanish Civil War, when the last of the Republican forces surrender. |
| 37180 | April 1 | Event | 1941 – Fântâna Albă massacre: Between 200 and 2,000 Romanian civilians are killed by Soviet Border Troops. |
| 37181 | April 1 | Event | 1941 – The Blockade Runner Badge for the German navy is instituted. |
| 37182 | April 1 | Event | 1941 – A military coup in Iraq overthrows the regime of 'Abd al-Ilah and installs Rashid Ali al-Gaylani as Prime Minister. |
| 37183 | April 1 | Event | 1944 – Navigation errors lead to an accidental American bombing of the Swiss city of Schaffhausen. |
| 37184 | April 1 | Event | 1945 – World War II: Operation Iceberg: United States troops land on Okinawa in the last major campaign of the war. |
| 37185 | April 1 | Event | 1946 – Aleutian Islands earthquake: An 8.6 magnitude earthquake near the Aleutian Islands creates a tsunami that strikes the Hawaiian Islands killing 159, mostly in Hilo. |
| 37186 | April 1 | Event | 1946 – Formation of the Malayan Union. |
| 37187 | April 1 | Event | 1947 – Paul becomes king of Greece, on the death of his childless elder brother, George II. |
| 37188 | April 1 | Event | 1947 – The only mutiny in the history of the Royal New Zealand Navy begins. |
| 37189 | April 1 | Event | 1948 – Cold War: Berlin Airlift: Military forces, under direction of the Soviet-controlled government in East Germany, set up a land blockade of West Berlin. |
| 37190 | April 1 | Event | 1948 – Faroe Islands gain autonomy from Denmark. |
| 37191 | April 1 | Event | 1949 – Chinese Civil War: The Chinese Communist Party holds unsuccessful peace talks with the Nationalist Party in Beijing, after three years of fighting. |
| 37192 | April 1 | Event | 1949 – The Government of Canada repeals Japanese Canadian internment after seven years. |
| 37193 | April 1 | Event | 1949 – The 26 counties of the Irish Free State become Ireland. |
| 37194 | April 1 | Event | 1954 – United States President Dwight D. Eisenhower authorizes the creation of the United States Air Force Academy in Colorado. |
| 37195 | April 1 | Event | 1955 – The EOKA rebellion against the British Empire begins in Cyprus, with the goal of obtaining the desired unification ("enosis") with Greece. |
| 37196 | April 1 | Event | 1957 – The BBC broadcasts the spaghetti-tree hoax on its current affairs programme Panorama. |
| 37197 | April 1 | Event | 1959 – Iakovos is enthroned as Greek Orthodox Archbishop of America. |
| 37198 | April 1 | Event | 1960 – The TIROS-1 satellite transmits the first television picture from space. |
| 37199 | April 1 | Event | 1960 – Dr. Martens released its first boots, the model 1460. |
| 37200 | April 1 | Event | 1967 – The United States Department of Transportation begins operation. |