The Gregorian calendar is the internationally accepted civil calendar. It was first proposed by the Calabrian doctor Aloysius Lilius, and decreed by Pope Gregory XIII, after whom the calendar was named, on 24 February 1582 by the papal bull Inter gravissimas. It was adopted later that year by a handful of countries, with other countries adopting it over the following centuries.
It is a reform of the Julian calendar. Gregory's bull does not ordain...
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The Gregorian calendar is the internationally accepted civil calendar. It was first proposed by the Calabrian doctor Aloysius Lilius, and decreed by Pope Gregory XIII, after whom the calendar was named, on 24 February 1582 by the papal bull Inter gravissimas. It was adopted later that year by a handful of countries, with other countries adopting it over the following centuries.
It is a reform of the Julian calendar. Gregory's bull does not ordain any particular year-numbering system, but uses the Anno Domini system which counts years from the traditional Incarnation of Jesus, and which had spread throughout Europe during the Middle Ages. That is the same year-numbering system that is the de facto international standard today.
The Gregorian calendar modifies the Julian calendar's regular cycle of leap years, years exactly divisible by four, including all centurial years, as follows:
Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible...
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