April 17 is the 107th day of the year (108th in leap years) in the Gregorian calendar. There are 258 days remaining until the end of the year.
1080 - King Harald III of Denmark dies and is succeeded by King Canute IV of Denmark, who later became the first Dane to be canonized.
1397 – Geoffrey Chaucer tells the Canterbury Tales for the first time at the court of Richard II.
1521 – Martin Luther speaks to the assembly at the Diet of Worms, refusing to recant his teachings.
1524 – Giovanni da Verrazano reaches New York harbor.
1861 – American Civil War: Virginia secedes from the Union.
1864 – American Civil War: Battle of Plymouth begins – Confederate forces attack Plymouth, North Carolina.
1865 – Mary Surratt is arrested as a conspirator in the assassination of Abraham Lincoln.
1882 – Copies of Pat Garrett's biography of Billy the Kid, An Authentic Life of Billy the Kid, arrive at the Library of Congress.
1895 – The Treaty of Maguan (also known as 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 , Taiwan and the Pescadores Islands.
1907 - The Ellis Island immigration center processes 11,747 people, more than any other day.
1912 - Russian troops shoot striking goldfield workers in Northeastern Siberia, killing at least 50.
1924 – Metro-Goldwyn-Mayer studios is formed from a merger of Metro Pictures, Goldwyn Pictures, and the Louis B. Mayer Company.
1937 – Daffy Duck first appears in Warner Bros' short Porky's Duck Hunt.
1941 – World War II: The Kingdom of Yugoslavia surrenders to Germany.
1946 – Syria gains full independence from France.
1969 - British passenger steamer 'Sir Harvey Adamson' disappears without a trace after leaving Rangoon, Burma, with 269 people on board.
1969 – Sirhan Sirhan is convicted of assassinating Robert F. Kennedy.
1970 – Apollo program: The ill-fated Apollo 13 spacecraft returns to Earth safely.
1975 – Cambodian Civil War ends: The Khmer Rouge captures the capital Phnom Penh and Cambodian government forces surrender.
2013 - The funeral of Margaret Thatcher takes place in London.