| 44221 | April 16 | Holiday and observance | Emancipation Day (Washington, D.C.) |
| 44222 | April 17 | Event | 1080 – The King of Denmark, Harald III dies and is succeeded by Canute IV, who would later be the first Dane to be canonized. |
| 44223 | April 17 | Event | 1349 – Fall of the Bavand dynasty, and rise of the Afrasiyab dynasty. |
| 44224 | April 17 | Event | 1397 – Geoffrey Chaucer tells The Canterbury Tales for the first time at the court of Richard II. Chaucer scholars have also identified this date (in 1387) as the start of the book's pilgrimage to Canterbury. |
| 44225 | April 17 | Event | 1492 – Spain and Christopher Columbus sign the Capitulations of Santa Fe for his voyage to Asia to acquire spices. |
| 44226 | April 17 | Event | 1521 – Trial of Martin Luther over his teachings begins during the assembly of the Diet of Worms. Initially intimidated, he asks for time to reflect before answering and is given a stay of one day. |
| 44227 | April 17 | Event | 1524 – Giovanni da Verrazzano reaches New York harbor. |
| 44228 | April 17 | Event | 1555 – After 18 months of siege, Siena surrenders to the Florentine-Imperial army. The Republic of Siena is incorporated into the Grand Duchy of Tuscany. |
| 44229 | April 17 | Event | 1797 – Sir Ralph Abercromby attacks San Juan, Puerto Rico, in what would be one of the largest invasions of the Spanish territories in America. |
| 44230 | April 17 | Event | 1797 – Citizens of Verona, Italy, begin an eight-day rebellion against the French occupying forces, which will end unsuccessfully. |
| 44231 | April 17 | Event | 1861 – The state of Virginia's secession convention votes to secede from the United States, becoming the 8th state to join the Confederate States of America. |
| 44232 | April 17 | Event | 1863 – American Civil War: Grierson's Raid begins – troops under Union Army Colonel Benjamin Grierson attack central Mississippi. |
| 44233 | April 17 | Event | 1864 – American Civil War: The Battle of Plymouth begins – Confederate forces attack Plymouth, North Carolina. |
| 44234 | April 17 | Event | 1895 – The Treaty of Shimonoseki between China and Japan is signed. This marks the end of the First Sino-Japanese War, and the defeated Qing Empire is forced to renounce its claims on Korea and to concede the southern portion of the Fengtien province, Tai |
| 44235 | April 17 | Event | 1897 – The Aurora, Texas, UFO incident |
| 44236 | April 17 | Event | 1905 – The Supreme Court of the United States decides Lochner v. New York, which holds that the "right to free contract" is implicit in the due process clause of the Fourteenth Amendment to the United States Constitution. |
| 44237 | April 17 | Event | 1907 – The Ellis Island immigration center processes 11,747 people, more than on any other day. |
| 44238 | April 17 | Event | 1912 – Russian troops open fire on striking goldfield workers in northeast Siberia, killing at least 150. |
| 44239 | April 17 | Event | 1937 – Daffy Duck's first appearance, in Porky's Duck Hunt. |
| 44240 | April 17 | Event | 1941 – World War II: The Kingdom of Yugoslavia surrenders to Germany. |
| 44241 | April 17 | Event | 1942 – French prisoner of war General Henri Giraud escapes from his castle prison in Königstein Fortress. |
| 44242 | April 17 | Event | 1944 – Forces of the Communist-controlled Greek People's Liberation Army attack the smaller National and Social Liberation resistance group, which surrenders. Its leader Dimitrios Psarros is murdered. |
| 44243 | April 17 | Event | 1945 – World War II: Brazilian forces liberate the town of Montese, Italy, from Nazi forces. |
| 44244 | April 17 | Event | 1946 – Syria obtains its independence from the French occupation. |
| 44245 | April 17 | Event | 1949 – At midnight 26 Irish counties officially leave the British Commonwealth. A 21-gun salute on O'Connell Bridge, Dublin, ushers in the Republic of Ireland. |
| 44246 | April 17 | Event | 1951 – The Peak District becomes the United Kingdom's first National Park. |
| 44247 | April 17 | Event | 1961 – Bay of Pigs Invasion: A group of Cuban exiles financed and trained by the CIA lands at the Bay of Pigs in Cuba with the aim of ousting Fidel Castro. |
| 44248 | April 17 | Event | 1964 – Jerrie Mock becomes the first woman to circumnavigate the world by air. |
| 44249 | April 17 | Event | 1964 – Ford Mustang is introduced to the North American market. |
| 44250 | April 17 | Event | 1969 – Sirhan Sirhan is convicted of assassinating Robert F. Kennedy. |