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Gregorian calendar Also called Gregorian
The civil calendar used by this form; its leap-year rule differs from the older Julian calendar.
In this entry Meaning Word origin How we know Connected concepts Sources Word origin · etymology Eponym.
Named after Pope Gregory XIII, who promulgated the calendar reform in 1582. Gregorian is the adjectival form of his name.
US Naval Observatory: Calendars, Explanatory Supplement ↗
How we know · epistemology Civil calendar convention
Gregorian arithmetic follows a defined leap-year rule. Historical documents did not adopt it everywhere at once, so a correctly calculated proleptic date may differ from the date originally recorded.
US Naval Observatory: Julian dates ↗
Connected concepts Mentioned in 5 other entries Sources & provenance Use the citations beside each section to distinguish a calculation convention, a historical teaching and an editorial example.
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US Naval Observatory: Julian dates ↗ US Naval Observatory: Calendars, Explanatory Supplement ↗ Start with Astrology → A definition explains a term. Its tradition and calculation settings determine how to use it.