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Our Western Calendar
Wikipedia Notice The Material on this Page is taken from articles published by Wikipedia. Citations to the original sources are given. According to Wikipedia standards, the notice printed below must be included when copying Wikipedia material: "This article is licensed under the GNU Free Documentation License, which means that you can copy and modify it as long as the entire work (including additions) remains under this license", and provide a link to http://www.gnu.org/copyleft/fdl.html. Julian calendar
From Wikipedia, the free encyclopedia The Julian calendar was introduced in 46 BC by Julius Caesar and came into force in 45 BC (709 ab urbe condita). It was chosen after consultation with the astronomer Sosigenes of Alexandria and was probably designed to approximate the tropical year, known at least since Hipparchus. It has a regular year of 365 days divided into 12 months, and a leap day is added to February every four years. Hence the Julian year is on average 365.25 days long. The notation "Old Style" (OS) is sometimes used to indicate a date in the Julian calendar, as opposed to "New Style" (NS), which either represents the Julian date with the start of the year as 1 January or a full mapping onto the Gregorian calendar. Although the Julian calendar remained in use into the 20th century in some countries and is still used by many national Orthodox churches, it has generally been replaced for civil use by the modern Gregorian calendar. Orthodox Churches no longer using the Julian calendar typically use the Revised Julian calendar rather than the Gregorian calendar. Reform was required because too many leap days are added with respect to the astronomical seasons on the Julian scheme. On average, the astronomical solstices and the equinoxes advance by about 11 minutes per year against the Julian year, causing the calendar to gain a day about every 134 years. While Hipparchus and presumably Sosigenes were aware of the discrepancy, although not of its correct value, it was evidently felt to be of little importance. However, it accumulated significantly over time, and eventually led to the reform of 1582, which replaced the Julian calendar with the more accurate Gregorian calendar. Year numbering The dominant method that the Romans used to identify a year for dating purposes was to name it after the two consuls who took office in it. Since 153 BC, they had taken office on 1 January, and Julius Caesar did not change the beginning of the year. Thus this consular year was an eponymous or named year. In addition to consular years, the Romans sometimes used the regnal year of the emperor, and by the late fourth century documents were also being dated according to the 15-year cycle of the indiction. In 537, Justinian required that henceforth the date must include the name of the emperor, in addition to the indiction and the consul. Only rarely did the Romans number the year from the founding of the city (of Rome), ab urbe condita (AUC). This method was used by Roman historians to determine the number of years from one event to another, not to date a year. Different historians had several different dates for the founding. The Fasti Capitolini, an inscription containing an official list of the consuls which was published by Augustus, used an epoch of 752 BC. The epoch used by Varro, 753 BC, has been adopted by modern historians. Indeed, Renaissance editors often added it to the manuscripts that they published, giving the false impression that the Romans numbered their years. Most modern historians tacitly assume that it began on the day the consuls took office, and ancient documents such as the Fasti Capitolini which use other AUC systems do so in the same way. However, Censorinus, writing in the third century AD, states that, in his time, the AUC year began with the Parilia, celebrated on 21 April, which was regarded as the actual anniversary of the foundation of Rome. Because the festivities associated with the Parilia conflicted with the solemnity of Lent, which was observed until the Saturday before Easter Sunday, the early Roman church did not celebrate Easter after 21 April.[3] While the Julian reform applied originally to the Roman calendar, many of the other calendars then used in the Roman Empire were aligned with the reformed calendar under Augustus. This led to the adoption of several local eras for the Julian calendar, such as the Era of Actium and the Spanish Era, some of which were used for a considerable time. Perhaps the best known is the Era of Martyrs, sometimes also called Anno Diocletiani (after Diocletian), which was often used by the Alexandrian Christians to number their Easters during the fourth and fifth centuries and continued to be used by the Coptic and Abyssinian churches. In the Eastern Mediterranean, the efforts of Christian chronographers such as Annianus of Alexandria to date the Biblical creation of the world led to the introduction of Anno Mundi eras based on this event. The most important of these was the Aetos Kosmou, used throughout the Byzantine world from the 10th century and in Russia till 1700. In the West, Dionysius Exiguus proposed the system of Anno Domini in 525. This era gradually spread through the western Christian world, once the system was adopted by Bede. Proleptic Julian calendar
From Wikipedia, the free encyclopedia The proleptic Julian calendar is produced by extending the Julian calendar to dates preceding AD 4 when its quadrennial leap year stabilized. The leap years actually observed between its official implementation in 45 BC and AD 4 were erratic, see the Julian calendar article for details. A calendar obtained by extension earlier in time than its invention or implementation is called the "proleptic" version of the calendar, and thus we obtain the proleptic Julian calendar. Likewise, the proleptic Gregorian calendar is occasionally used to specify dates before its official introduction in 1582. Because the Julian calendar was actually used before that time, one must explicitly state that a given date is in the proleptic Gregorian calendar when that is used. Historians since Bede have traditionally represented the years preceding AD 1 as "1 BC", "2 BC", etc. Bede and later Latin writers chose not to place the Latin zero, nulla, between BC and AD years. In this system the year 1 BC would be a leap year. To determine an interval in years across the BC/AD boundary, it is more convenient to include a year zero and represent earlier years as negative. This is the convention used in the "astronomical Julian calendar". In this system the year 0 is equivalent to 1 BC and is a leap year. (http://en.wikipedia.org/wiki/Proleptic_Julian_calendar) |