January 21:
A.D. 1077: German King Heinrich (Henry) IV petitions Pope Gregory VII for absolution of his excommunication.
A.D. 1189: The Third Crusade is begun by Richard Cœur de Lion, Phillip II, and Henry II.
A.D. 1793: Louis XVI is guillotined in Paris.
A.D. 1799: Edward Jenner's smallpox vaccine is introduced.