Papal legates lay a bull of excommunication on the altar of Hagia Sophia, marking the split between Roman Catholic and Eastern Orthodox churches.
Date given in the Julian calendar.
William of Normandy defeats King Harold II, beginning the Norman conquest of England.
The Seljuks defeat and capture Byzantine Emperor Romanos IV, opening Anatolia to Turkish settlement.
During the Investiture Controversy, Emperor Henry IV goes to Canossa to seek absolution from Pope Gregory VII.
Ibn Sina (Avicenna) completes The Canon of Medicine, a medical encyclopedia used as a standard text in the Islamic world and Europe for centuries.
William I orders a great survey of land and property across England, recorded in the Domesday Book.
Traditionally founded in 1088, the University of Bologna is regarded as the oldest university in continuous operation.