Editing May 21 (section)

===Pre-1600===
* [[293]] &ndash; Roman Emperors [[Diocletian]] and [[Maximian]] appoint [[Galerius]] as ''[[Caesar (title)|Caesar]]'' to Diocletian, beginning the period of four rulers known as the [[Tetrarchy]].
* [[878]] &ndash; [[Syracuse, Sicily]], is [[Siege of Syracuse (877–878)|captured]] by the Muslim [[Aghlabids]] after a nine-month siege.
* [[879]] &ndash; [[Pope John VIII]] gives blessings to [[Branimir of Croatia]] and to the [[Croatia]]n people, considered to be international recognition of the Croatian state.<ref>{{cite book|last=Preveden|first=Francis Ralph|title=A History of the Croatian People from Their Arrival on the Shores of the Adriatic to the Present Day: Prehistory and Early Period Until 1397 A.D|location=New York|publisher=Philosophical Library|date=1962|oclc=906081868|page=58}}</ref>
* [[996]] &ndash; Sixteen-year-old [[Otto III, Holy Roman Emperor|Otto III]] is crowned [[Holy Roman Emperor]].<ref>{{cite book|last=Hill|first=David Jayne|title=A History of Diplomacy in the International Development of Europe. Vol. 1: The Struggle for Universal Empire|location=New York|publisher=Longmans, Green & Co.|date=1911|oclc=557420|url=https://books.google.com/books?id=F3HFAAAAMAAJ|pages=189–190}}</ref>
*[[1349]] &ndash; [[Dušan's Code]], the constitution of the [[Serbian Empire]], is enacted by [[Dušan the Mighty]].
*[[1403]] &ndash; [[Henry III of Castile]] sends [[Ruy González de Clavijo]] as [[Timurid relations with Europe|ambassador to Timur]] to discuss the possibility of an alliance between Timur and Castile against the [[Ottoman Empire]].
*[[1554]] &ndash; [[Mary I of England|Queen Mary I]] grants a [[royal charter]] to [[Derby School]], as a grammar school for boys in [[Derby]], England.