Europe

• Pietro Tradonico
  Pietro Tradonico
  Pietro Tradonico , an Istrian by birth, was the Doge of Venice from 836 to 864. He was, according to tradition, the thirteenth doge, though historically he is only the eleventh. His election broke the power of the Participazio. He was illiterate, and forced to sign all state documents with the...
  
   is elected Doge of Venice
  Doge of Venice
  The Doge of Venice , often mistranslated Duke was the chief magistrate and leader of the Most Serene Republic of Venice for over a thousand years. Doges of Venice were elected for life by the city-state's aristocracy. Commonly the person selected as Doge was the shrewdest elder in the city...
  
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• Uen
  Uen of the Picts
  Uuen [Wen] or Eogán in Gaelic was king of the Picts, or of Fortriu , in what is now Scotland....
  
   succeeds Drest IV
  Drest IV of the Picts
  Drest son of Girom was a king of the Picts.The Pictish Chronicle king lists associate him with Drest III. Various reigns, separately and jointly, are assigned to the two Drests, varying from one to fifteen years...
  
   as king of the Picts
  Picts
  The Picts were a group of Late Iron Age and Early Mediaeval people living in what is now eastern and northern Scotland. There is an association with the distribution of brochs, place names beginning 'Pit-', for instance Pitlochry, and Pictish stones. They are recorded from before the Roman conquest...
  
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• Saracens from Egypt attack the Italian
  Italy
  Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
  
   city
  City
  A city is a relatively large and permanent settlement. Although there is no agreement on how a city is distinguished from a town within general English language meanings, many cities have a particular administrative, legal, or historical status based on local law.For example, in the U.S...
  
   of Naples
  Naples
  Naples is a city in Southern Italy, situated on the country's west coast by the Gulf of Naples. Lying between two notable volcanic regions, Mount Vesuvius and the Phlegraean Fields, it is the capital of the region of Campania and of the province of Naples...
  
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• Vikings from Scandinavia
  Scandinavia
  Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
  
   attack Constantinople
  Constantinople
  Constantinople was the capital of the Roman, Eastern Roman, Byzantine, Latin, and Ottoman Empires. Throughout most of the Middle Ages, Constantinople was Europe's largest and wealthiest city.-Names:...
  
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Astronomy

• April 10 – Comet Halley
  Comet Halley
  Halley's Comet or Comet Halley is the best-known of the short-period comets, and is visible from Earth every 75 to 76 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth, and thus the only naked-eye comet that might appear twice in a human lifetime...
  
   passes approximately 5 million km
  1 E9 m
  To help compare different distances this page lists lengths starting at 109 metres .Distances shorter than 109 metres* 1.4 Gm — Diameter of Sun...
  
  from Earth – its closest ever approach to Earth.