|Covid-19|February – Battle of Mortemer: The Normans defeat a French army, as it is caught pillaging and plundering. King Henry I of France withdraws his main army from Normandy as a result.
April 30 – The earliest known European tornado strikes Rosdalla, Kilbeggan (Ireland).
July 4 – The SN 1054 supernova is recorded by the Chinese, Arab and possibly Native Americans, near the star Zeta Tauri. For 23 days it remains bright enough to be seen in daylight. Its remnants form the Crab Nebula (NGC 1952).
July 16 – Cardinal Humbertus, a representative of the newly deceased Pope Leo IX, and Michael Cerularius, Patriarch of Constantinople, decree each other excommunicated. Most historians look to this act as the final step in the initiation of the Great Schism between the Roman Catholic and Orthodox Christian Churches (In 1965, those excommunications will be rescinded by Pope Paul VI and Patriarch Athenagoras, when they meet in the Second Vatican Council. However, to this day each church claims to be the One Holy Catholic and Apostolic Church, and each denies the other's right to that name) (See East–West Schism).
July 27 – Siward, Earl of Northumbria invades Scotland, to support Malcolm Canmore against Macbeth, who usurped the Scottish throne from Malcolm's father, King Duncan. Macbeth is defeated at Dunsinane.
Lý Nhật Tôn, third king of the Lý dynasty, begins to rule in Vietnam, and changes the country's official name to Đại Việt.
The Almoravids retake the trading center of Awdaghost from Ghana
Al-Hariri of Basra (d. 1122), Arab poet and scholar
February 20 – Yaroslav the Wise, prince of Kievan Rus'
April 19 – Pope Leo IX (b. 1002)
September 24 – Hermannus Contractus, German scholar, composer, music theorist, mathematician, and astronomer
Year 1054 (MLIV) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar.
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