September 12
day of the year
September 12 is the 255th day of the year (256th in leap years) in the Gregorian calendar; 110 days remain until the end of the year.
Events
Pre-1600
490 BC – Battle of Marathon: The conventionally accepted date for the Battle of Marathon. The Athenians and their Plataean allies defeat the first Persian invasion force of Greece.
372 – Sixteen Kingdoms: Sima Yao, age 10, succeeds his father Emperor Jianwen as Emperor Xiaowu of the Eastern Jin dynasty.
1185 – Isaac Angelos is crowned Byzantine emperor following the deposition of Andronikos I Komnenos and after the crowd rejects the coronation of Isaac's uncle John Doukas.
1213 – Albigensian Crusade: Simon de Montfort, 5th Earl of Leicester, defeats Peter II of Aragon at the Battle of Muret.
1229 – Battle of Portopí: The Aragonese army under the command of James I of Aragon disembarks at Santa Ponça, Mallorca, with the purpose of conquering the island.
1297 – The Treaty of Alcañices, mediated by the pope, between the king Denis of Portugal and king Ferdinand IV of Castile defines the border between the two countries and establishes an alliance of friendship.
1309 – The first siege of Gibraltar takes place in the context of the Spanish Reconquista, pitting the forces of the Kingdom of Castile against the Emirate of Granada and resulting in a Castilian victory.
1601–1900
1609 – Henry Hudson begins his exploration of the Hudson River while aboard the Halve Maen.
This brief starts where responsible research should: with the source description of “September 12” as day of the year. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
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.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Sep 18, 2026. The linked authority identifier is Q2849. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1600, 1185, 1213 and 1229.
The absence of detail may reflect summary conventions rather than a lack of surviving documentation. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “September 12” 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.