|823 by topic|
|Ab urbe condita||1576|
|Balinese saka calendar||744–745|
|Chinese calendar||壬寅年 (Water Tiger)|
3519 or 3459
— to —
癸卯年 (Water Rabbit)
3520 or 3460
|- Vikram Samvat||879–880|
|- Shaka Samvat||744–745|
|- Kali Yuga||3923–3924|
|Japanese calendar||Kōnin 14|
|Minguo calendar||1089 before ROC|
|Seleucid era||1134/1135 AG|
|Thai solar calendar||1365–1366|
949 or 568 or −204
— to —
950 or 569 or −203
- Emperor Michael II defeats the rebel forces under Thomas the Slav in Thrace. He and his supporters are forced to seek refuge in Arkadiopolis (modern Turkey). After five months of blockade, Thomas surrenders and is delivered to Michael, seated on a donkey and bound in chains. He pleads for clemency and prostrates before Michael, but is executed.
- 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).
- 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.
- 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.
- June 13 – Charles the Bald, king of the Franks (d. 877)
- Ermentrude of Orléans, queen of the Franks (d. 869)
- Muhammad I, Muslim emir of Córdoba (d. 886)
- Pepin II (the Younger), king of Aquitaine
- Adelochus, archbishop of Strasbourg (b. 786)
- Boniface I, margrave of Tuscany
- Ceolwulf I, king of Mercia (approximate date)
- Gondulphus, bishop of Metz
- Han Hong, general of the Tang Dynasty b. 765)
- Ljudevit, duke of the Slavs in Lower Pannonia
- Thekla, Byzantine empress (approximate date)
- Thomas the Slav, Byzantine general and usurper
- Timothy I, Syrian patriarch
- Wulfheard, bishop of Hereford (approximate date)
- Bury, John Bagnell (1912). A History of the Eastern Roman Empire from the Fall of Irene to the Accession of Basil I (A.D. 802–867). London: Macmillan and Company. pp. 105–106. OCLC 458995052.
- Treadgold, Warren (1988). The Byzantine Revival, 780–842. Stanford, California: Stanford University Press. pp. 241–242. ISBN 978-0-8047-1462-4.
- "Charles II | Holy Roman emperor". Encyclopedia Britannica. Retrieved November 27, 2020.