1: 1st Christmas, according to calendar-maker Dionysus Exiguus

800: Pope Leo III crowns Charles the Great (Charlemagne), Roman Emperor

1066: William the Conqueror is crowned King of England at Westminster Abbey, completing the Norman conquest of England

1741: Astronomer Anders Celsius introduces Centigrade temperature scale

1868: Despite bitter opposition, US President Andrew Johnson grants unconditional pardon to all persons involved in Southern rebellion (Civil War)

1991: Mikhail Gorbachev formally resigns as President of USSR in a televised speech

Source: Onthisday.com