Events

• Succession of Pope Valentine, then Pope Gregory IV.
• Arabs invade Sicily.
• The royal ceremonial centre at Copán is abandoned.
• Chalid Ben Abdulmelik and Ali Ben Isa measure the size of the Earth.

Births

• Saint Cyril, scholar, theologian, and linguist (d. 869)
• Emperor Montoku of Japan (d. 858)

Deaths

• Pope Eugene II
• September: Pope Valentine