Julian calendar

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Julian calendar

chronology

Also known as: Old Style calendar

Written and fact-checked by The Editors of Encyclopaedia Britannica

Last Updated: Mar 9, 2024 • Article History

Julius Caesar

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Category: Science & Tech

Also called:: Old Style calendar

Key People:: Julius Caesar; Sosigenes of Alexandria

Related Topics:: calendar

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Julian calendar, dating system established by Julius Caesar as a reform of the Roman republican calendar. By the 40s bce the Roman civic calendar was three months ahead of the solar calendar. Caesar, advised by the Alexandrian astronomer Sosigenes, introduced the Egyptian solar calendar, taking the length of the solar year as 365 1/4 days. The year was divided into 12 months, all of which had either 30 or 31 days except February, which contained 28 days in common (365 day) years and 29 in every fourth year (a leap year, of 366 days). Leap years repeated February 23; ...(100 of 301 words)

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