Year 1420 (MCDXX) was a leap year starting on Monday (link will display the full calendar) of the Julian calendar. Events of 1420 May 21 – Treaty of Troyes: With the Burgundian faction dominant in France, King Charles VI of France acknowledges Henry V of England as his heir and as virtual ruler of most of France. May 25 – Henry the Navigator's appointed governor of the Order of Christ. June 7 – Troops of the Republic of Venice capture Udine after a long siege, ending the… (More on 1420)