Historedia
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Issuance of Inter gravissimas

When
24 February 1582
Where
Papal States
Part of
Implementation of the Gregorian Calendar by Pope Gregory XIII

Pope Gregory XIII issued the papal bull Inter gravissimas on 24 February 1582, formally instituting the Gregorian calendar as a replacement for the Julian calendar.

The bull was dated 24 February 1582 and served as the legal instrument for the reform. It established the new calendar within the Catholic Church and the Papal States, where Gregory XIII held supreme religious and civil authority.

Sources

  1. Pope Gregory XIII Wikipedia, revision of 2026-07-11
  2. Gregorian calendar Wikipedia, revision of 2026-09-11

Machine-drafted from the cited Wikipedia passages and checked by a reviewing model, not by a human editor. Every passage cites the revision it was written from; dates and places follow those passages.