# Canonical recap data for Gregorian Calendar Adopted by Papacy (1582)
# Source: https://recap.at/1582/gregorian-calendar-reform
# Format: YAML 1.2 (UTF-8). Generated at request time.
slug: gregorian-calendar-reform
canonicalUrl: "https://recap.at/1582/gregorian-calendar-reform"
title: Gregorian Calendar Adopted by Papacy
subtitle: Pope Gregory XIII's calendar reform corrected the Julian calendar's drift, establishing the timekeeping system used worldwide today.
recapType: global_event
eventStatus: concluded
startDate: 1582-01-01
datePrecision: year
year: 1582
decade: 1580
country:
name: Vatican City
slug: vatican-city
summaryShort: The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull Inter gravissimas issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years slightly di
summaryLong: The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull Inter gravissimas issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years slightly differently to make the average calendar year 365.2425 days long rather than the Julian calendar's 365.25 days, thus more closely approximating the 365.2422-day "tropical" or "solar" year that is determined by the Earth's revolution around the Sun.
heroImageUrl: "https://upload.wikimedia.org/wikipedia/commons/thumb/8/89/Gregorianscher_Kalender_Petersdom.jpg/1280px-Gregorianscher_Kalender_Petersdom.jpg"
heroImageCredit: "Camillo Rusconi (1658–1728); photograph de:User:Rsuessbr · via Wikipedia"
importance: 84
sourceConfidence: 75
keyFacts: []
timeline: []
sources:
- url: "https://en.wikipedia.org/wiki/Gregorian_calendar"
  title: Gregorian calendar
  provider: Wikipedia
related: []
categories:
- launch
metaDescription: The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull Inter gravissimas issued by
wikidataQid: Q12138
archiveSnapshots:
- url: "https://web.archive.org/web/20260628170419/https://en.wikipedia.org/wiki/Gregorian_calendar"
  capturedAt: 2026-06-28
  label: Gregorian calendar
  originalUrl: "https://en.wikipedia.org/wiki/Gregorian_calendar"
taxonomy:
domain: religious
eventTypes:
- ideological_manifesto
canonicalClasses:
- creation
- transformation
impactRadius: global
velocity: gradual
predictability: scheduled
intentionality: planned
domainCoupling: multi_domain
lifecycleClass: birth
