| 1 April 1204 | Anjou, France [births and deaths] | Eleanor of Aquitaine, Queen Consort first of King Louis VII of France, then of King Henry II of England, mother of King Richard I the Lionheart and King John of England, and one of the most influential women in 12th-century Europe, dies in Fontevrault, Anjou, France (c. 82). |
| 1 April 1257 | Holy Roman Empire [political events] | Four members of the College of Seven Electors elect King Alfonso X of Castile and León as King of the Romans. |
| 1 April 1509 | Spain, France, Holy Roman Empire, Venice, Italy [political events] | The League of Cambrai (an alliance of Spain, France, and the Holy Roman Empire) declares war on Venice, intending to deprive the Venetian Republic of its territories on the Italian mainland. |
| 1–22 April 1572 | Spanish Netherlands, Holy Roman Empire [Dutch Revolt (1598–1609)] | The Watergeuzen (‘Sea Beggars’), Protestant rebel privateers led by Count Lumey van der Mark, capture the small ports of Brill in Holland and, on 22 April, Vlissingen in Zeeland, with the aid of an insurgent populace; these become the first permanent bases for the Dutch Revolt against Spanish Habsburg rule. |
| 1 April 1581 | Spain, Portugal [political events] | King Philip II of Spain and I of Portugal promises the Cortes (parliament) at Thomar that he will uphold Portuguese liberties and laws and administer the kingdom through the Portuguese civil service. Apart from the abolition of customs tolls on the Castilian border, Portugal and its colonies remain autonomous. |
| 1 April 1605 | Papal States, Italy [political events] | Alessandro Ottaviano de' Medici is elected Pope Leo XI following the death of Clement VIII on 5 March; however, he dies on 27 April. Camillo Borghese is elected Pope Paul V on 16 May. |
| 1 April 1686 | Holy Roman Empire, Habsburg Monarchy, Brandenburg, Germany [diplomacy] | An alliance between the Holy Roman Emperor Leopold I and Frederick William, the Great Elector of Brandenburg, is signed. By its terms, Brandenburg promises to support Habsburg claims in Spain and to provide assistance against French aggression. In return for the territory of Schwiebus, Brandenburg also renounces her claims to Silesia. |
| 1 April 1815 | German Empire, Brandenburg [births and deaths] | Otto von Bismarck, founder and first chancellor of the German Empire 1871–90, born in Schönhausen, Brandenburg (–1898). |
| 1 April 1852 | Burma, UK [wars] | The Second Anglo-Burmese War breaks out after the expiry of a British ultimatum to the king of Burma to pay compensation to British merchants following disputes between the traders and local inhabitants. |
| 1 April 1867 | Southeast Asia [colonies and mandate] | The rule of the British East India Company in the Straits Settlements province (comprising Singapore, Malacca, Penang, Cocos Islands, Christmas Island, and Labuan) ends as it becomes a British crown colony, its residents having become unhappy at government from India. |
| 1 April 1873 | Russia [births and deaths] | Sergey Vasilevich Rachmaninov, Russian composer and piano virtuoso, born in Oneg, near Semenovo, Russia (–1943). |
| 1 April 1889 | France [elections] | General Georges Boulanger, fearing trial for treason, flees from France. In the subsequent elections the Republicans triumph. |
| 1 April 1950 | Italian Somaliland, British Somaliland, UK, Italy [colonies and mandate] | Italian Somaliland, occupied by British troops from 1941 to 1949, becomes a United Nations (UN) trust territory under Italian administration, but most of modern Somalia (British Somaliland) continues as a British protectorate until 1960. |
| 1 April 1960 | UK [consumer products] | R Griggs & Co. begin to produce Doc Martens boots under licence in Britain. |
| 1 April 1970 | North Vietnam, South Vietnam [Vietnam War (1954–75)] | The Vietcong launch major assaults throughout South Vietnam after a six-month lull. |
| 1 April 1970 | USA [radio] | President Richard M Nixon signs a bill banning cigarette advertising on US radio and television. This takes effect the following year. |
| 1 April 1972 | UK [family planning] | Hounslow Borough Council in London, England, is the first local authority to offer free contraceptives to residents. |
| 1 April 1973 | USA [information technology] | A committee of grocers and manufacturers recommends the use of Universal Product Codes (UPC) (bar codes) on items sold in grocery stores. The codes will permit electronic scanning of items, reduce cashier error, and improve stock control; a few stores use it from 1974 and it comes into general use in the USA in 1980. |
| 1 April 1974 | UK [family planning] | Free contraception is made universally available on the National Health Service in Britain. |
| 1 April 1979 | Iran [law and government] | Following a referendum, Iran is declared an Islamic Republic by the Shiite Muslim leader Ayatollah Khomeini. |
| 1 April 1991 | USA [births and deaths] | Martha Graham, US choreographer of modern dance, dies in New York City (96). |
