Julian calendar Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! === Context of the reform === Although the approximation of {{frac|365|1|4}} days for the tropical year had been known for a long time,<ref>{{cite journal|first=R. A.|last=Parker|title=Ancient Egyptian Astronomy|journal=Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences|volume=276|issue=1257|date=May 1974|pages=51–65|jstor=74274}}</ref> ancient [[solar calendar]]s had used less precise periods, resulting in gradual misalignment of the calendar with the seasons. The [[octaeteris]], a cycle of eight [[Lunar calendar|lunar years]] popularised by [[Cleostratus]] (and also commonly attributed to [[Eudoxus of Cnidus|Eudoxus]]) which was used in some early Greek calendars, notably in [[Attic calendar|Athens]], is 1.53 days longer than eight [[Julian year (astronomy)|mean Julian years]]. The length of nineteen years in the [[Metonic cycle|cycle of Meton]] was 6,940 days, six hours longer than the mean Julian year. The mean Julian year was the basis of the [[Callippic cycle|76-year cycle]] devised by [[Callippus]] (a student under Eudoxus) to improve the Metonic cycle. In Persia (Iran) after the reform in the [[Iranian calendars#Old Persian calendar|Persian calendar]] by introduction of the Persian Zoroastrian (i. e. Young Avestan) calendar in 503 BC and afterwards, the first day of the year (1 Farvardin=[[Nowruz]]) slipped against the [[March equinox|vernal equinox]] at the rate of approximately one day every four years.<ref>Hartner, Willy. "The young Avestan and Babylonian calendars and the antecedents of precession." Journal for the History of Astronomy 10 (1979): 1. pp. 1–22. [[doi:10.1177/002182867901000102]]</ref><ref>Stern, Sacha. ''Calendars in antiquity: Empires, states, and societies''. Oxford University Press, 2012., p. 178.</ref> Likewise in the [[Egyptian calendar]], a fixed year of 365 days was in use, drifting by one day against the sun in four years. An unsuccessful attempt to add an extra day every fourth year was made in 238 BC ([[Decree of Canopus]]). Caesar probably experienced this "wandering" or "vague" calendar in that country. He landed in the Nile delta in October 48 BC and soon became embroiled in the Ptolemaic dynastic war, especially after [[Cleopatra VII|Cleopatra]] managed to be "introduced" to him in [[Alexandria]]. Caesar imposed a peace, and a banquet was held to celebrate the event.<ref name="Book 10">Lucan, ''[[Pharsalia]]:'' [http://mcllibrary.org/Pharsalia/book10.html ''Book 10''.]</ref> [[Lucan]] depicted Caesar talking to a wise man called [[Acoreus]] during the feast, stating his intention to create a calendar more perfect than that of Eudoxus<ref name="Book 10" /> (Eudoxus was popularly credited with having determined the length of the year to be {{frac|365|1|4}} days).<ref>Émile Biémont, ''Rythmes du temps, astronomie et calendriers'', éd. De Boeck (Bruxelles), 2000 ({{ISBN|2-8041-3287-0}}), p. 224.</ref> But the war soon resumed and Caesar was attacked by the Egyptian army for several months until he achieved victory. He then enjoyed a long cruise on the Nile with Cleopatra before leaving the country in June 47 BC.<ref>Suetonius, [https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Suetonius/12Caesars/Julius*.html#52 ''Caesar'' 52.1.] {{Webarchive|url=https://archive.today/20120530163202/http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Suetonius/12Caesars/Julius*.html#52 |date=2012-05-30 }}</ref> Caesar returned to Rome in 46 BC and, according to [[Plutarch]], called in the best philosophers and mathematicians of his time to solve the problem of the calendar.<ref>Plutarch, [https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Plutarch/Lives/Caesar*.html#59 ''Lives of the Noble Grecians and Romans'': Caesar 59].</ref> Pliny says that Caesar was aided in his reform by the astronomer [[Sosigenes of Alexandria]]<ref>Pliny, ''Natural History:'' [https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137%3Abook%3D18%3Achapter%3D57 ''(Book 18, LVII)''.]</ref> who is generally considered the principal designer of the reform. Sosigenes may also have been the author of the astronomical almanac published by Caesar to facilitate the reform.<ref>Encyclopædia Britannica [https://www.britannica.com/EBchecked/topic/555018/Sosigenes-of-Alexandria Sosigenes of Alexandria].</ref> Eventually, it was decided to establish a calendar that would be a combination between the old Roman months, the fixed length of the Egyptian calendar, and the {{frac|365|1|4}} days of Greek astronomy. According to Macrobius, Caesar was assisted in this by a certain Marcus Flavius.<ref>Macrobius, [https://penelope.uchicago.edu/Thayer/L/Roman/Texts/Macrobius/Saturnalia/1*.html#14.2 ''Saturnalia'' I.14.2] (Latin).</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. 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