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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.
Caesar's calendar became the predominant calendar in the Roman Empire and subsequently most of the Western world for more than 1,600 years, until 1582 when Pope Gregory XIII promulgated a revised calendar. The Julian calendar has two types of years: a normal year of 365 days and a leap year of 366 days.
In 45 BCE, Julius Caesar introduced a significant reform known as the Julian calendar. This new system aimed to resolve the inaccuracies of the earlier Roman calendar by aligning it with the solar year.
Żeby ponownie zsynchronizować kalendarz z porami roku, rok 708 a.u.c. wydłużono o 80 dni. Był to „annus confusionis” (łac. rok zamieszania), liczył 445 dni [2]. Kalendarz juliański ustalał długość roku na 365 dni oraz jeden dzień dodatkowy co 4 lata, w latach przestępnych. Średnia długość roku wynosiła 365,25 dnia.
The Roman calendar was reformed by Julius Caesar in 45 BC. The Julian calendar was no longer dependent on the observation of the new moon but simply followed an algorithm of introducing a leap day every four years. This created a dissociation of the calendar month from the lunation.
Learn how the Gregorian calendar, introduced in 1582, corrected the inaccuracies of the Julian calendar and why some countries skipped days when they switched. See the table of calendar reform dates and the conversion between the two systems.
Learn about the Julian calendar, a solar calendar introduced by Julius Caesar in 45 BCE to replace the lunar Roman calendar. Find out how it works, why it was replaced by the Gregorian calendar, and how it is still used in some cultures and fields.