April 15

• April 15, 1205
  Bulgaria under Emperor Kaloyan beats and captures the Latin Emperor Baldwin I at the Battle of Adrianople
• April 15, 1450
  French defeat English at Battle of Formigny in Hundred Years War
• April 15, 1452
  Leonardo da Vinci, an Italian painter, sculptor, scientist and visionary, is born in Vinci near Florence
• April 15, 1469
  Guru Nanak, the founder of the religion of Sikhism, is born
• April 15, 1472
  Leon Battista Alberti, Italian humanist, architect, writes his classic architectural treatise De Re Aedificatoria
• April 15, 1738
  The first bottle opener is invented by unknown person
• April 15, 1874
  The Societe Anonyme Cooperative des Artistes Peintres, Sculpteurs, and Graveurs, better known today as the Impressionists organize and present their first public group exhibition at the Paris studio of the photographer Nadar
• April 15, 1892
  General Electric is formed by the merger of the Edison Electric Light Co. and other firms in New York State
• April 15, 1896
  The first modern Olympic Games are closed in Athens
• April 15, 1931
  The Castellammarese War ends with the assassination of Joe "The Boss" Masseria, briefly leaving Salvatore Maranzano as capo di tutti i capi and undisputed ruler of the American Mafia
• April 15, 1936
  Assailants shot two Jewish drivers during an attack on a convoy of trucks on the Nablus to Tulkarm road, starting Arab Revolt against the British in purpose to oppose Jewish immigration in Palestine
• April 15, 1947
  Jackie Robinson becomes the first African American to play in the major leagues in the modern era
• April 15, 1989
  The death of Hu Yaobang, a high-ranking official of the People's Republic of China, sparks the beginning of the Tiananmen Square protests in Beijing, China
• April 15, 1996
  The treasure of Primos found by Heinrich Schliemann in 1873 in Troy and taken from Berlin in 1945 by Russians is exhibited in Moscow for the first time
• April 15, 2013
  Two Chechen Islamist brothers explode two bombs at the Boston Marathon in Boston, Massachusetts, in the United States, killing 3 and injuring 264 others