May 21
day of the year
May 21 is the 141st day of the year (142nd in leap years) in the Gregorian calendar; 224 days remain until the end of the year.
Events
Pre-1600
293 – Roman Emperors Diocletian and Maximian appoint Galerius as Caesar to Diocletian, beginning the period of four rulers known as the Tetrarchy.
878 – Syracuse, Sicily, is captured by the Muslim Aghlabids after a nine-month siege.
879 – Pope John VIII gives blessings to Branimir of Croatia and to the Croatian people, considered to be international recognition of the Croatian state.
996 – Sixteen-year-old Otto III is crowned Holy Roman Emperor.
1294 – Coronation of Michael IX Palaiologos as Byzantine Emperor.
1347 – Coronation of John VI Kantakouzenos as Byzantine Emperor by patriarch Isidore I of Constantinople at the Church of St. Mary of Blachernae.
1349 – Dušan's Code, the constitution of the Serbian Empire, is enacted by Dušan the Mighty.
1403 – 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.
This brief starts where responsible research should: with the source description of “May 21” as day of the year. Everything that follows is an evidence route, not borrowed authority.
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The subject matters to the general reference register because the source frames it as day of the year. Its deeper value depends on whether names, dates, institutions and citations support that framing.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 23, 2026. The linked authority identifier is Q2580. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1600, 1294, 1347 and 1349.
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This entry incorporates text from “May 21” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.