📅 Today in HistoryMay 20
The First Council of Nicaea is formally opened, starting the first ecumenical council of the Christian Church.
Empress Ariadne marries Anastasius I. The widowed Augusta is able to choose her successor for the Byzantine throne, after Zeno (late emperor) dies of dysentery.
The Battle of Dun Nechtain is fought between a Pictish army under King Bridei III and the invading Northumbrians under King Ecgfrith, who are decisively defeated.
While visiting the royal Mercian court at Sutton Walls with a view to marrying princess Ælfthryth, King Æthelberht II of East Anglia is taken captive and beheaded.
The Second Battle of Lincoln is fought near Lincoln, England, resulting in the defeat of Prince Louis of France by William Marshal, 1st Earl of Pembroke.
King Sancho IV of Castile creates the Estudio de Escuelas de Generales in Alcalá de Henares.
The Battle of Alfarrobeira is fought, establishing the House of Braganza as a principal royal family of Portugal.
John Cabot sets sail from Bristol, England, on his ship Matthew looking for a route to the west (other documents give a May 2 date).
Portuguese explorer Vasco da Gama discovers the sea route to India when he arrives at Kozhikode (previously known as Calicut), India.
