On This Day: May 21st

Queen Mary I grants a royal charter to Derby School, as a grammar school for boys in Derby, England.

Coronation of James I of Scotland at Scone.

Henry III of Castile sends Ruy González de Clavijo as ambassador to Timur to discuss the possibility of an alliance between Timur and Castile against the Ottoman Empire.

Dušan's Code, the constitution of the Serbian Empire, is enacted by Dušan the Mighty.

Coronation of John VI Kantakouzenos as Byzantine Emperor by patriarch Isidore I of Constantinople at the Church of St. Mary of Blachernae.

Coronation of Michael IX Palaiologos as Byzantine Emperor.

Sixteen-year-old Otto III is crowned Holy Roman Emperor.

Pope John VIII gives blessings to Branimir of Croatia and to the Croatian people, considered to be international recognition of the Croatian state.

Syracuse, Sicily, is captured by the Muslim Aghlabids after a nine-month siege.

Roman Emperors Diocletian and Maximian appoint Galerius as Caesar to Diocletian, beginning the period of four rulers known as the Tetrarchy.