[Wikipedia] April 21: Monarchy of the United Kingdom

  The monarchy of the United Kingdom is a system of government in which 
  a hereditary monarch is the sovereign of the United Kingdom and its 
  overseas territories.  The terms British monarch and British monarchy 
  may mean different things in different contexts beyond the United 
  Kingdom.  The present monarch is Queen Elizabeth II, who has reigned 
  since 6 February, 1952.  The heir apparent is her eldest son, Charles, 
  Prince of Wales and Duke of Rothesay.  They and the Queen's husband and 
  consort, Prince Philip, Duke of Edinburgh, undertake various public 
  duties in accordance with their positions.  Elizabeth II is Head of the 
  Commonwealth and also reigns as head of state of 15 other Commonwealth 
  countries.  This developed from the former colonial relationship of 
  these countries to Britain, but they are now independent and the 
  monarchy of each is legally distinct.  

Read the rest of this article:
  http://en.wikipedia.org/wiki/Monarchy_of_the_United_Kingdom

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Today's selected anniversaries:

1836:
  Texan forces led by Sam Houston defeated General Antonio López de 
  Santa Anna and his Mexican troops in the Battle of San Jacinto near La 
  Porte, the decisive battle in the Texas Revolution.  
  (http://en.wikipedia.org/wiki/Battle_of_San_Jacinto)

1894:
  Norway formally adopted the Krag-Jørgensen, a repeating bolt action 
  rifle designed by the Norwegians Ole Herman Johannes Krag and Erik 
  Jørgensen, as the main firearm of its armed forces.