August 21

• August 21, 1680
  Pueblo Indians take possession of Santa Fe and drives the Spanish out of New Mexico until 1692 during the Pueblo Revolt
• August 21, 1770
  British navigator, James Cook formally claims the East Coast of Australia for Great Britain, naming it New South Wales during his first voyage
• August 21, 1808
  Napoleon Bonaparte's General Jean-Andoche Junot is defeated by British General Arthur Wellesley at the first Battle of the Peninsular War at Vimeiro, Portugal
• August 21, 1810
  Sweden's Riksdag elects Jean-Baptiste Bernadotte, Marshal of France under Napoleon, as heir apparent to the Swedish throne
• August 21, 1841
  John Hampson of New Orleans patents the Window blind
• August 21, 1944
  Dumbarton Oaks conference, which establishes United Nations, opens in Washington, DC
• August 21, 1968
  Radio Prague, Czechoslovakia, at 12:50 AM announces a Soviet-led invasion, after Warsaw Pact forces enter Czechoslovakia to end reform movement known as Prague Spring
• August 21, 1986
  A limnic eruption at Lake Nyos in Cameroon triggers the sudden release of about 200,000 tons of carbon dioxide and causes death of 1,744 people
• August 21, 2013
  1,429 are killed in the Ghouta chemical attack during the Syrian Civil War, blamed on President Bashar al-Assad

April 17

• April 17, 69
  Roman emperor Marcus Salvius Otho commits suicide after being defeated by Vitellius' troops in battle of Bedriacum in North-Italy
• April 17, 1421
  Dikes at Dort Holland breaks after a heavy storm near the North Sea coast which results in 10,000 drown
• April 17, 1492
  A contract is signed by Christopher Columbus and a representative of Spain's King Ferdinand and Queen Isabella, giving Columbus a commission to seek a westward ocean passage to find the Indies
• April 17, 1524
  Giovanni da Verrazzano, a Florentine navigator in the service of the King Francis I of France, discovers New York Bay in America
• April 17, 1534
  Sir Thomas More, an English lawyer and social philosopher, is jailed in the Tower of London by order of Henry VIII
• April 17, 1732
  The second Kamchatka Expedition with Vitus Bering as captain commander is announced in the Russian Senate to include astronomical and scientific observations, and explore the seas between Siberia and Japan
• April 17, 1758
  Francis Williams, the first African-American to graduate for a college in the western hemisphere, publishes a collection of Latin poems
• April 17, 1817
  The first American School for the deaf is founded by Thomas Hopkins Gallaudet and Laurent Clerc in Hartford, Connecticut
• April 17, 1824
  The Russo-American Treaty of 1824 recognized exclusive Russian rights to the fur trade above Latitude 54°, 40' North, with the American rights and claims restricted to below that line
• April 17, 1875
  The game of "snooker" is invented by Sir Neville Francis Fitzgerald Chamberlain, a British Army officer
• April 17, 1895
  China and Japan sign the peace treaty of Shimonoseki, followed a war over control of the Korean peninsula, by which China recognizes independence and autonomy of Korea and cedes to Japan the Taiwan
• April 17, 1956
  Cominform, the first official forum of the international communist movement, is dissolves
• April 17, 1961
  1,400 Cuban exiles, funded by the United States government's Central Intelligence Agency, land in Bay of Pigs and attempt to overthrow Fidel Castro
• April 17, 1964
  The Ford Motor Company unveils the Ford Mustang at the New York World's Fair, US$2368 base price
• April 17, 1969
  Czechoslovakia's Communist Party chairman Alexander Dubcek deposed
• April 17, 1975
  Phnom Penh, the capital of Cambodia, falls to Communist insurgents of Khmer Rouge, ending Cambodia's five-year Civil War and starting cruel Pol Pot regime
• April 17, 2004
  Israeli helicopters fire missiles at a convoy of vehicles in the Gaza Strip, killing the Gaza leader of Hamas, Abdel Aziz al-Rantissi