20th day events in history

August 20, 14 Agrippa Postumus, adopted son of the late Roman emperor Augustus, is executed by his guards while in exile under mysterious circumstances
December 20, 69 Vespasian, formerly a general under Nero, enters Rome to claim the title of Emperor
July 20, 70 Siege of Jerusalem – Titus, son of emperor Vespasian, storms the Fortress of Antonia north of the Temple Mount. The Roman army is drawn into street fights with the Zealots
December 20, 217 The papacy of Zephyrinus ends. Callixtus I is elected as the sixteenth pope, but is opposed by the theologian Hippolytus who accuses him of laxity and of being a Modalist, one who denies any distinction between the three persons of the Trinity
March 20, 235 Maximinus Thrax is proclaimed emperor. He is the first foreigner to hold the Roman throne
January 20, 250 Emperor Decius begins a widespread persecution of Christians in Rome. Pope Fabian is martyred
November 20, 284 Diocletian is chosen as Roman emperor
May 20, 325 The First Council of Nicea – the first Ecumenical Council of the Christian Church is held
June 20, 451 Battle of Chalons: Flavius Aetius' battles Attila the Hun. After the battle, which was inconclusive, Attila retreats, causing the Romans to interpret it as a victory
May 20, 491 Empress Ariadne marries Anastasius I. The widowed Augusta is able to choose her successor for the Byzantine throne, after Zeno (late emperor) dies of dysentery
May 20, 526 An earthquake kills about 250,000 people in what is now Syria and Antiochia
September 20, 622 Muhammad and Abu Bakr arrived Medina
August 20, 636 Battle of Yarmouk: Arab forces led by Khalid ibn al-Walid take control of Syria and Palestine away from the Byzantine Empire, marking the first great wave of Muslim conquests and the rapid advance of Islam outside Arabia
January 20, 649 King Chindasuinth, at the urging of bishop Braulio of Zaragoza, crowns his son Recceswinth as co-ruler of the Visigothic Kingdom
March 20, 673 Emperor Tenmu of Japan assumes the Chrysanthemum throne at the Palace of Kiyomihara in Asuka
May 20, 685 The Battle of Dun Nechtain is fought between a Pictish army under King Bridei III and the invading Northumbrians under King Ecgfrith, who are decisively defeated
November 20, 762 During the An Shi Rebellion, the Tang dynasty, with the help of Huihe tribe, recaptures Luoyang from the rebels
July 20, 911 Rollo lays siege to Chartres
August 20, 917 Battle of Acheloos: Tsar Simeon I of Bulgaria decisively defeats a Byzantine army
August 20, 1000 The foundation of the Hungarian state by Saint Stephen, celebrated as a National Day in Hungary
September 20, 1058 Agnes of Poitou and Andrew I of Hungary meet to negotiate about the border-zone in present-day Burgenland
September 20, 1066 Battle of Fulford, Viking Harald Hardrada defeats earls Morcar and Edwin
August 20, 1083 Canonization of the first King of Hungary, Saint Stephen and his son Saint Emeric
September 20, 1187 Saladin begins the Siege of Jerusalem
July 20, 1189 Richard I of England officially invested as Duke of Normandy
December 20, 1192 Richard I of England is captured and imprisoned by Leopold V of Austria on his way home to England after signing a treaty with Saladin ending the Third Crusade
November 20, 1194 Palermo is conquered by Henry VI, Holy Roman Emperor
March 20, 1206 Michael IV Autoreianos is appointed Ecumenical Patriarch of Constantinople
June 20, 1214 The University of Oxford receives its Royal charter
May 20, 1217 The Second Battle of Lincoln is fought near Lincoln, England, resulting in the defeat of Prince Louis of France by William Marshal, 1st Earl of Pembroke
September 20, 1260 The Great Prussian Uprising among the old Prussians begins against the Teutonic Knights
January 20, 1265 In Westminster, the first English parliament conducts its first meeting held by Simon de Montfort in the Palace of Westminster, now also known colloquially as the "Houses of Parliament"
May 20, 1293 King Sancho IV of Castile creates the Study of General Schools of Alcalá
April 20, 1303 The Sapienza University of Rome is instituted by Pope Boniface VIII
July 20, 1304 Wars of Scottish Independence: Fall of Stirling Castle – King Edward I of England takes the stronghold using the War Wolf
August 20, 1308 Pope Clement V pardons Jacques de Molay, the last Grand Master of the Knights Templar, absolving him of charges of heresy
January 20, 1320 Duke Wladyslaw Lokietek becomes king of Poland
February 20, 1339 The Milanese army and the St. George's (San Giorgio) Mercenaries of Lodrisio Visconti clashed in the Battle of Parabiago
January 20, 1356 Edward Balliol abdicates as King of Scotland
September 20, 1378 Cardinal Robert of Geneva, called by some the "Butcher of Cesena", is elected as Avignon Pope Clement VII, beginning the Papal schism
August 20, 1391 Konrad von Wallenrode becomes the 24th Hochmeister of the Teutonic Order
July 20, 1402 Ottoman-Timurid Wars: Battle of Ankara – Timur, ruler of Timurid Empire, defeats forces of the Ottoman Empire sultan Bayezid I
November 20, 1407 A truce between John the Fearless, Duke of Burgundy and Louis of Valois, Duke of Orléans is agreed upon under the auspices of John, Duke of Berry. Orléans would be assassinated three days later by Burgundy
May 20, 1449 The Battle of Alfarrobeira is fought, establishing the House of Braganza as a principal royal family of Portugal
April 20, 1453 The last naval battle in Byzantine history occurs, as three Genoese galleys escorting a Byzantine transport fight their way through the huge Ottoman blockade fleet and into the Golden Horn
August 20, 1467 The Second Battle of Olmedo takes places as part of a succession conflict between Henry IV of Castile and his half-brother Alfonso, Prince of Asturias
February 20, 1472 Orkney and Shetland are pawned by Norway to Scotland in lieu of a dowry for Margaret of Denmark
May 20, 1497 John Cabot sets sail from Bristol, England, on his ship Matthew looking for a route to the west (other documents give a May 2 date)
May 20, 1498 Portuguese explorer Vasco da Gama discovers the sea route to India when he arrives at Kozhikode (previously known as Calicut), India
September 20, 1498 The 1498 Nankai earthquake generates a tsunami that washes away the building housing the statue of the Great Buddha at Kōtoku-in in Kamakura, Kanagawa, Japan; since then the Buddha has sat in the open air