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! == Julian reform == === Realignment of the year === [[File:Retrato de Julio César (26724093101) (cropped).jpg|thumb|upright|The [[Tusculum portrait]] of [[Julius Caesar]]]] The first step of the reform was to realign the start of the calendar year (1 January) to the tropical year by making 46 BC 445 days long, compensating for the intercalations which had been missed during Caesar's pontificate. This year had already been extended from 355 to 378 days by the insertion of a regular [[intercalary month]] in February. When Caesar decreed the reform, probably shortly after his return from the [[Battle of Thapsus|African campaign]] in late Quintilis (July), he added 67 more days by inserting two extraordinary intercalary months between November and December.<ref group="note">It is not known why he decided that 67 was the correct number of days to add, nor whether he intended to align the calendar to a specific astronomical event such as the winter solstice. [[Ideler]] suggested (''Handbuch der mathematischen und technischen Chronologie'' II 123–125) that he intended to align the winter solstice to a supposedly traditional date of 25 December. The number may compensate for three omitted intercalary months (67 = 22+23+22). It also made the distance from 1 March 46 BC, the original New Year's Day in the Roman calendar, to 1 January 45 BC 365 days.</ref> These months are called ''Intercalaris Prior'' and ''Intercalaris Posterior'' in letters of [[Cicero]] written at the time; there is no basis for the statement sometimes seen that they were called "[[Undecimber]]" and "[[Duodecember|Duodecimber]]", terms that arose in the 18th century over a millennium after the Roman Empire's collapse.<ref group="note">E.g., "... we have a sidelight on what was involved in "the year of confusion" as it was called. According to Dion Cassius, the historian, there was a governor in Gaul who insisted that, in the lengthened year, two months' extra taxes should be paid. The extra months were called Undecimber and Duodecimber." (P. W. Wilson, [https://books.google.com/books?id=9xcbAAAAYAAJ&q=undecimber+duodecimber ''The romance of the calendar''] (New York, 1937), 112). The eponymous dating of the cited passage ([https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Cassius_Dio/54*.html#21 Dio Cassius 54.21]) shows that it actually refers to an event of 15 BC, not 46 BC.</ref> Their individual lengths are unknown, as is the position of the [[Nones (calendar)|Nones]] and [[Ides (calendar)|Ides]] within them.<ref>J. Rüpke, ''The Roman Calendar from Numa to Constantine: Time, History and the Fasti'', 117f., suggests, based on the ritual structures of the calendar, that 5 days were added to November and that the two intercalary months each had 31 days, with Nones and Ides on the 7th and 15th.</ref> Because 46 BC was the last of a series of irregular years, this extra-long year was, and is, referred to as the "last year of confusion". The new calendar began operation after the realignment had been completed, in 45 BC.<ref>[[William Smith (lexicographer)|William Smith]], ''[[Dictionary of Greek and Roman Antiquities]]:'' [https://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA*/Calendarium.html#p231 Year of Julius Caesar], following [[Ideler]], interprets Macrobius, [https://penelope.uchicago.edu/Thayer/L/Roman/Texts/Macrobius/Saturnalia/1*.html#14.13 ''Saturnalia'' 1.14.13] (Latin) to mean that Caesar decreed that the first day of the new calendar began with the new moon which fell on the night of 1/2 January 45 BC. <br /> The new moon was on 2 January 45 BC (in the [[Proleptic Julian calendar]]) at 00:21 UTC, according to [[Institut de mécanique céleste et de calcul des éphémérides|IMCCE]] (a branch of the [[Paris Observatory]]): [http://bugle.imcce.fr/en/grandpublic/phenomenes/phases_lune/index.php ''Phases of the moon (between −4000 and +2500)''] {{webarchive|url=https://web.archive.org/web/20110720232543/http://bugle.imcce.fr/en/grandpublic/phenomenes/phases_lune/index.php|date=2011-07-20}}. This is in agreement with the [http://astropixels.com/ephemeris/phasescat/phases-0099.html historical moon phase tables by Fred Espenak] in which the new moon was on 2 January 45 BC at 00:43 UTC. Espenek's table assumes that the first Julian year of 45 BC was a leap year. If the first year of 45 BC was not a leap year, there would be a day offset, and the new moon would have been on 1 January 45 BC at 00:43 UTC. <br /> Espnek's historical moon phase tables also indicate that there was a new moon on 1 March 45 BC at 08:39 UTC ([[Calends|Kalends]] of March), quarter moon on 8 March 45 BC at 09:00 UTC (a day after [[Roman calendar#Days|Nones of March]]), and full moon on 15 March 45 BC at 07:19 UTC ([[Ides of March]]). Espenak's tables of the phases of the moon are based on computational procedures described in ''Astronomical Algorithms'' by [[Jean Meeus]] (Willmann-Bell, Inc., Richmond, 1998). <br /> More recent studies of the Macrobius manuscripts have shown that the word on which Idler's supposition is based, which was read as ''lunam'', should be read as ''linam'', meaning that Macrobius was simply stating that Caesar published an edict giving the revised calendar – see e.g., p.99 in the translation of Macrobius by P. Davies. <br /> Smith gives no source or justification for his other speculation that Caesar originally intended to commence the year precisely with the winter solstice.</ref> === Months === The Julian months were formed by adding ten days to a regular pre-Julian Roman year of 355 days, creating a regular Julian year of 365 days. Two extra days were added to January, Sextilis (August) and December, and one extra day was added to April, June, September, and November. February was not changed in ordinary years, and so continued to be the traditional 28 days. Thus, the ordinary (i.e., non-leap year) lengths of all of the months were set by the Julian calendar to the same values they still hold today. The Julian reform did not change [[Roman calendar#Months|the method used to account days of the month in the pre-Julian calendar]], based on the Kalends, Nones and Ides, nor did it change the positions of these three dates within the months. Macrobius states that the extra days were added immediately before the last day of each month to avoid disturbing the position of the established religious ceremonies relative to the Nones and Ides of the month.<ref>Macrobius, [https://penelope.uchicago.edu/Thayer/L/Roman/Texts/Macrobius/Saturnalia/1*.html#14.9 ''Saturnalia'' 1.14.9] (Latin). Exceptionally, the extra day in April was inserted as the 26th, a.d. VI Kal. Mai. in the Julian calendar, in order to avoid adding a day to the [[Floralia]], which ran from a.d. IV Kal. Mai. (27 April in the pre-Julian calendar) to a.d. V Non. Mai.</ref> The inserted days were all initially characterised as ''dies fasti'' ('''F''' – see [[Roman calendar#Character of the day|Roman calendar]]).<ref>Macrobius, [https://penelope.uchicago.edu/Thayer/L/Roman/Texts/Macrobius/Saturnalia/1*.html#14.12 ''Saturnalia'' 1.14.12] (Latin).</ref> The character of a few festival days was changed. In the early Julio-Claudian period a large number of festivals were decreed to celebrate events of dynastic importance, which caused the character of the associated dates to be changed to '''NP'''. However, this practice was discontinued around the reign of [[Claudius]], and the practice of characterising days fell into disuse around the end of the first century AD: the Antonine jurist [[Gaius (jurist)|Gaius]] speaks of ''dies nefasti'' as a thing of the past.<ref>A. K. Michels, ''The Calendar of the Roman Republic'' Appendix II; J. Rüpke, ''The Roman Calendar from Numa to Constantine'' 113–114, 126–132, 147.</ref> === Intercalation === The old intercalary month was abolished. The new leap day was dated as ''ante diem bis sextum Kalendas Martias'' ('the sixth doubled day before the Kalends of March'), usually abbreviated as ''a.d. bis VI Kal. Mart.''; hence it is called in English the [[bissextile]] day. The year in which it occurred was termed ''annus bissextus'', in English the bissextile year. There is debate about the exact position of the bissextile day in the early Julian calendar. The earliest direct evidence is a statement of the 2nd century jurist [[Publius Iuventius Celsus|Celsus]], who states that there were two-halves of a 48-hour day, and that the intercalated day was the "posterior" half. An inscription from AD 168 states that ''a.d. V Kal. Mart.'' was the day after the bissextile day. The 19th century chronologist [[Christian Ludwig Ideler|Ideler]] argued that Celsus used the term "posterior" in a technical fashion to refer to the earlier of the two days, which requires the inscription to refer to the whole 48-hour day as the bissextile. Some later historians share this view. Others, following [[Theodor Mommsen|Mommsen]], take the view that Celsus was using the ordinary Latin (and English) meaning of "posterior". A third view is that neither half of the 48-hour "bis sextum" was originally formally designated as intercalated, but that the need to do so arose as the concept of a 48-hour day became obsolete.<ref>W. Sternkopf, "[https://books.google.com/books?id=MmPMaTG2ukYC&pg=PA718 Das Bissextum]", (JCP 41 (1895) 718–733).</ref> There is no doubt that the bissextile day eventually became the earlier of the two days for most purposes. In 238 Censorinus stated that it was inserted after the [[Terminus (god)|Terminalia]] (23 February) and was followed by the last five days of February, i.e., a.d. VI, V, IV, III and prid. Kal. Mart. (which would be 24 to 28 February in a common year and the 25th to 29th in a leap year). Hence he regarded the bissextum as the first half of the doubled day. All later writers, including Macrobius about 430, [[Bede]] in 725, and other medieval [[computus|computists]] (calculators of Easter) followed this rule, as does the [[liturgical year|liturgical calendar]] of the Roman Catholic Church. However, Celsus' definition continued to be used for legal purposes. It was incorporated into [[Digest (Roman law)|Justinian's Digest]],<ref>Justinian, [http://webu2.upmf-grenoble.fr/Haiti/Cours/Ak/Anglica/D50_Scott.htm#XVI Digest 50.16.98] {{Webarchive|url=https://web.archive.org/web/20120208135740/http://webu2.upmf-grenoble.fr/Haiti/Cours/Ak/Anglica/D50_Scott.htm#XVI |date=2012-02-08 }}.</ref> and in the English ''[[Statute De Anno et Die Bissextili]]'' of 1236,<ref>{{cite book |chapter-url=https://books.google.com/books?id=tKZFAAAAcAAJ&pg=PA20 |chapter=The statute ''De anno et die bissextili'', made at Westminster, Anno 21 Hen. III. and Anno Dom. 1236 |title=The Statutes at Large from Magna Charta to the End of the Reign of King Henry the Sixth |volume=1 |location=London |year=1763}}</ref> which was not formally repealed until 1879. The effect of the bissextile day on the [[nundinal cycle]] is not discussed in the sources. According to Dio Cassius, a leap day was inserted in 41 BC to ensure that the first market day of 40 BC did not fall on 1 January, which implies that the old 8-day cycle was not immediately affected by the Julian reform. However, he also reports that in AD 44, and on some previous occasions, the market day was changed to avoid a conflict with a religious festival. This may indicate that a single nundinal letter was assigned to both halves of the 48-hour bissextile day by this time, so that the [[Regifugium]] and the market day might fall on the same date but on different days. In any case, the 8-day nundinal cycle began to be displaced by the 7-day [[Seven-day week|week]] in the first century AD, and [[dominical letter]]s began to appear alongside nundinal letters in the fasti.<ref>[https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Cassius_Dio/48*.html#33.4 Dio Cassius 48.33.4], [https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Cassius_Dio/60*.html#24.7 60.24.7]; C. J. Bennett, "The Imperial Nundinal Cycle", ''Zeitschrift für Papyrologie und Epigraphik'' 147 (2004) 175–179.</ref> ===Year length; leap years=== The Julian calendar has two types of year: "normal" years of 365 days and [[leap year|"leap" years]] of 366 days. There is a simple cycle of three "normal" years followed by a leap year and this pattern repeats forever without exception. The Julian year is, therefore, on average 365.25 days long. Consequently, the Julian year drifts over time with respect to the [[tropical year|tropical (solar) year]] (365.24217 days).<ref name="Richards">Using value from Richards (2013, p. 587) for tropical year in mean solar days, the calculation is {{nowrap|1/(365.2425-365.24217)}}</ref> Although Greek astronomers had known, at least since [[Hipparchus]],<ref name=":0">[[Ptolemy|Claudius Ptolemy]], tr. [[G. J. Toomer]], ''[[Almagest|Ptolemy's Almagest]]'', 1998, Princeton University Press, p. 139. Hipparchus stated that the "solar year ... contains 365 days, plus a fraction which is less than {{sfrac|1|4}} by about {{sfrac|1|300}}th of the sum of one day and night".</ref> a century before the Julian reform, that the tropical year was slightly shorter than 365.25 days, the calendar did not compensate for this difference. As a result, the calendar year gains about three days every four centuries compared to observed [[equinox]] times and the seasons. This discrepancy was largely corrected by the [[Gregorian calendar|Gregorian reform]] of 1582. The Gregorian calendar has the same months and month lengths as the Julian calendar, but, in the Gregorian calendar, year numbers evenly divisible by 100 are not leap years, except that those evenly divisible by 400 remain leap years<ref name=":1">[http://aa.usno.navy.mil/faq/docs/calendars.php Introduction to Calendars] {{Webarchive|url=https://web.archive.org/web/20190613115330/http://aa.usno.navy.mil/faq/docs/calendars.php |date=2019-06-13 }}. (15 May 2013). [[United States Naval Observatory]].</ref> (even then, the Gregorian calendar diverges from astronomical observations by one day in 3,030 years).<ref name=Richards /> 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. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). 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