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The 820s

237 sourced entries across 10 years, inside the 9th century. Each year below opens its own page; the lines under it are that year’s highest-ranked entries.

820 CE31 entries

  • December 25 – Emperor Leo V (the Armenian) is assassinated by conspirators in the Hagia Sophia, at Constantinople. Though unarmed, he fights back fiercely but dies of his wounds. He is succeeded by Michael II, the commander of the palace guard (excubitores). Leo's family (including his mother and his wife Theodosia) are exiled to monasteries in Princes' Islands.
  • Emperor Xian Zong dies from poisoning (due to medicines), after a 14-year reign. He is succeeded by his son Mu Zong, as ruler of the Tang dynasty.
  • Fedelmid mac Crimthainn assumes the kingship as ruler of Munster (modern Ireland).

821 CE21 entries

  • February – Duke Borna of Croatia dies after an 11-year reign, as vassal of the Frankish Empire. He is succeeded by his nephew, Vladislav. Emperor Louis I recognizes him as prince of Dalmatia and Liburnia, at the Council of Aachen.
  • October – Lothair I, co-emperor and eldest son of Louis I, marries Ermengarde in Thionville (northeastern France). She is the daughter of Count Hugh of Tours.
  • Tahir ibn Husayn, an Iranian general, is appointed as governor of Khurasan, as a reward for supporting the Abbasid caliph al-Ma'mun in the Fourth Fitna.

822 CE24 entries

  • February 6 – Ukit Took becomes the last ruler (ajaw) of the Mayan city-state Copán (modern Guatemala). After his death in 830, the kingdom is wiped out, most likely from an epidemic.
  • Battle of Kedouktos (near Heraclea): Khan Omurtag of Bulgaria sends a relief army, and defeats the Byzantine rebels.
  • Emperor Louis I performs public penance for causing his nephew Bernard's death 4 years earlier, at his palace of Attigny (Ardennes), before Pope Paschal I, and the Frankish nobles (this to restore harmony and re-establish his authority).

823 CE16 entries

  • April 5 – Lothair I, eldest son of Emperor Louis I, is crowned co-emperor again by Pope Paschal I at Rome (initiating the papal practice of handing the imperial sword over, as a symbol of temporal power in the Holy Roman Empire).
  • May 30 – Emperor Saga abdicates the throne, after a 10-year reign. He is succeeded by his brother Junna, as the 53rd emperor of Japan.
  • King Ceolwulf I of Mercia is deposed by Beornwulf, who takes the throne of Mercia. During his rule he rebuilds the Abbey of St. Peter, and presides over two synods at Clofesho.

824 CE31 entries

  • March 3 – (9.19.13.15.19) (9th B'ak'tun, 19th K'atun, 13th year (Tun) 15th month (Winal) 19th day (K'in)) Juun Tsak-Took becomes the new ruler of the Mayan city state of Machaquila (in what is now Guatemala), along with co-ruler and Ti-Chaak become the after the death of Sihyaj K'in Ich’aak II. Juun Tsak-Tookwill until his 840.
  • September – Rebellious Arab troops in North Africa, led by Mansur ibn Nasr al-Tunbudhi in a battle against the Aghlabids, led by the Emir Ziyadat Allah, invade and occupy the city of Tunis.
  • November 11 – The Constitutio Romana, drawn up between King Lothair I of Italy, Louis the Pious, since 817, and Pope Eugene II, establishes the authority of the Holy Roman Emperors over the papacy of Rome.

825 CE24 entries

  • August - This year, on the first day of Chingam month, Kerala’s Kollam Era ( Malayalam Era/Calendar, also known as Kollavarsham) commences.
  • Battle of Ellandun: King Egbert of Wessex defeats Beornwulf of Mercia near Swindon. The battle marks the end of the Mercian domination of southern England. The kingdoms of Kent, Surrey, Sussex and Essex submit to Wessex, and East Anglia acknowledges Egbert as overlord (bretwalda).
  • Borobudur, a Mahayana Buddhist Temple, is completed in Central Java (modern Indonesia).

826 CE22 entries

  • May – Euphemius, Byzantine admiral, organises an uprising in Sicily against Emperor Michael II. He proclaims himself Emperor (with the title of basileus) in Syracuse, independent from Constantinople. In turn, Euphemius is defeated by Byzantine troops (reinforcements from the East), and is driven out to North Africa.
  • King Harald Klak of Denmark receives the Frisian county of Rüstringen, as a gift from Emperor Louis the Pious.
  • Prince Aethelwulf, a son of King Egbert of Wessex, invades Kent, and drives out its pro-Mercian king Baldred.

827 CE22 entries

  • June 14 – Euphemius, exiled Byzantine admiral, asks for the help of North African Arabs, to retake Sicily and Malta from the Byzantines. Emir Ziyadat Allah I of Ifriqiya promises to return the islands to Euphemius, in exchange for a yearly tribute, and sends an Arab Muslim expeditionary force of 10,000 men under the 70-year-old Asad ibn al-Furat, which lands at Mazara del Vallo in Sicily.
  • August 27 – Pope Eugene II dies after a 3-year reign, and is succeeded by Valentine as the 100th pope of the Catholic Church.
  • October 10 – Pope Valentine dies just after a two-month reign, and is succeeded by Gregory IV as the 101st pope of Rome.

828 CE20 entries

  • At the instigation of Adalram, archbishop of Salzburg, the first Christian church in Central and Eastern Europe is built in Nitra, Pannonia.
  • Relics of Mark the Evangelist are stolen from Alexandria (controlled by the Abbasid Caliphate) by two Venetian merchants, and brought to Venice.
  • In the capital of Chang'an, a powerful court eunuch orders 50 wrestlers to arrest 300 commoners over a land property dispute in Northwest Chang'an, whereupon a riot breaks out in the streets.

829 CE26 entries

  • October 2 – Emperor Michael II dies after an 8-year reign in Constantinople, and is succeeded by his 16-year-old son Theophilos, as sole emperor of the Byzantine Empire. He continues his father's ideology of iconoclasm.
  • The Bai kingdom of Nanzhao captures the city of Chengdu, in Sichuan Province.
  • Viking chieftain Halfdan the Black becomes king of Agder (modern Norway). He expands his realm through military conquest and political negotiations, dividing the kingdom of Vestfold with his half-brother Olaf.