Julian calendar

Julian calendar

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The Julian calendar began in 45 BC (709 AUC
Ab urbe condita
Ab urbe condita is Latin for "from the founding of the City ", traditionally set in 753 BC. AUC is a year-numbering system used by some ancient Roman historians to identify particular Roman years...

) as a reform of the Roman calendar
Roman calendar
The Roman calendar changed its form several times in the time between the founding of Rome and the fall of the Roman Empire. This article generally discusses the early Roman or pre-Julian calendars...

 by Julius Caesar
Julius Caesar
Gaius Julius Caesar was a Roman general and statesman and a distinguished writer of Latin prose. He played a critical role in the gradual transformation of the Roman Republic into the Roman Empire....

. It was chosen after consultation with the astronomer Sosigenes of Alexandria
Sosigenes of Alexandria
Sosigenes of Alexandria was named by Pliny the Elder as the astronomer consulted by Julius Caesar for the design of the Julian calendar. Little is known about him apart from Pliny's Natural History...

 and was probably designed to approximate the tropical year
Tropical year
A tropical year , for general purposes, is the length of time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth; for example, the time from vernal equinox to vernal equinox, or from summer solstice to summer solstice...

 (known at least since Hipparchus
Hipparchus
Hipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...

).

The Julian calendar has a regular year of 365 days divided into 12 months with a leap day added to February every four years. The Julian year is, therefore, on average 365.25 days long. The motivation for most calendars is to fix the number of days between return of the cycle of seasons (from spring equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...

 to the next spring equinox, for example), so that the calendar could be used as an aid to planting and other season-related activities. The cycle of seasons (tropical year) had been known since ancient times to be about 365 and 1/4 days long.

The more modern Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...

 eventually superseded the Julian calendar: the reason is that a tropical year (or solar year) is actually about 11 minutes shorter than 365.25 days. These extra 11 minutes per year in the Julian calendar caused it to gain about three days every four centuries, when compared to the observed equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...

 times and the seasons. In the Gregorian calendar system, first proposed in the 16th century, this problem was dealt with by dropping some calendar days, in order to realign the calendar and the equinox times. Subsequently, the Gregorian calendar drops three leap year days across every four centuries.

The Julian calendar remained in use into the 20th century in some countries as a civil calendar
Civil calendar
In any country, the civil calendar is the calendar, or possibly one of several calendars, used within that country for civil, official or administrative purposes. The civil calendar is almost always used for general purposes by people and private organizations....

, but has been replaced by the Gregorian calendar in nearly all countries. The Roman Catholic Church
Roman Catholic Church
The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with over a billion members. Led by the Pope, it defines its mission as spreading the gospel of Jesus Christ, administering the sacraments and exercising charity...

, the Eastern Rite Catholic Churches and Protestant churches have replaced the Julian calendar with the Gregorian calendar. However, the Orthodox Church still uses the Julian calendar for calculating the dates of moveable feast
Moveable feast
In Christianity, a moveable feast or movable feast is a holy day – a feast day or a fast day – whose date is not fixed to a particular day of the calendar year but moves in response to the date of Easter, the date of which varies according to a complex formula...

s, including Easter or Pascha. Some Orthodox churches have adopted the Revised Julian calendar
Revised Julian calendar
The Revised Julian calendar, also known as the Rectified Julian calendar, or, less formally, New calendar, is a calendar, originated in 1923, which effectively discontinued the 340 years of divergence between the naming of dates sanctioned by those Eastern Orthodox churches adopting it and the...

 for the observance of fixed feast
Fixed feast
A fixed feast is an annual celebration that is held on the same calendar date every year, such as Christmas, as distinguished from moveable feasts, such as Easter, whose calendar date varies....

s, while other Orthodox churches retain the Julian calendar for all purposes. The Julian calendar is still used by the Berber people
Berber people
Berbers are the indigenous peoples of North Africa west of the Nile Valley. They are continuously distributed from the Atlantic to the Siwa oasis, in Egypt, and from the Mediterranean to the Niger River. Historically they spoke the Berber language or varieties of it, which together form a branch...

 of North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...

, and on Mount Athos
Mount Athos
Mount Athos is a mountain and peninsula in Macedonia, Greece. A World Heritage Site, it is home to 20 Eastern Orthodox monasteries and forms a self-governed monastic state within the sovereignty of the Hellenic Republic. Spiritually, Mount Athos comes under the direct jurisdiction of the...

.

The notation "Old Style" (OS)
Old Style and New Style dates
Old Style and New Style are used in English language historical studies either to indicate that the start of the Julian year has been adjusted to start on 1 January even though documents written at the time use a different start of year ; or to indicate that a date conforms to the Julian...

 is sometimes used to indicate a date in the Julian calendar, as opposed to "New Style" (NS)
Old Style and New Style dates
Old Style and New Style are used in English language historical studies either to indicate that the start of the Julian year has been adjusted to start on 1 January even though documents written at the time use a different start of year ; or to indicate that a date conforms to the Julian...

, which either represents the Julian date with the start of the year as 1 January or a full mapping onto the Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...

. This notation is used in reference to dates from tsarist Russia (the country did not switch to the new calendar until 1918).

Table of months

Months Lengths before 45 BC Lengths as of 45 BC
Ianuarius
Ianuarius
The word "Ianuarius" is the original Roman designation of the month January.The name is either derived from the two-faced Roman god Janus, from the Latin word ianua, which means "door", or it is the masculine form of Diana, which would be Dianus or Ianus ....

 
29 31
Februarius  28 (leap years: 23 or 24) 28 (leap years: 29)
Martius
March
March is in present time held to be the third month of the year in both the Julian and Gregorian calendars. It is one of the seven months which are 31 days long....

 
31 31
April
April
April is the fourth month of the year in the Julian and Gregorian calendars, and one of four months with a length of 30 days. April was originally the second month of the Roman calendar, before January and February were added by King Numa Pompilius about 700 BC...

is
29 30
Maius  31 31
Iunius
Junius (month)
Junius was the Latin name for the fourth month in the Roman calendar that was before Quintilis.Iunius, or Junius, is named in honor of the ancient Roman goddess Juno, the wife of Jupiter and considered the patroness of marriage. The first half of Iunius is a period of religious purification, and...

 
29 30
Quintilis
Quintilis
In the 10-month calendar of ancient Rome, Quintilis follows Junius and precedes Sextilis . Quintilis is Latin for "fifth", that is, it was the fifth month in the earliest calendar attributed to Romulus, which began with the month of Martius...

 (Iulius)
31 31
Sextilis
Sextilis
Sextilis was the original Latin name for the sixth month in the Roman calendar. It was renamed Augustus in 8 BC in honor of the first Roman emperor, Augustus Caesar, for two reasons...

 (August
August
August is the eighth month of the year in the Julian and Gregorian Calendars and one of seven months with a length of 31 days.This month was originally named Sextilis in Latin, because it was the sixth month in the original ten-month Roman calendar under Romulus in 753 BC, when March was the first...

us)
29 31
September
September
September is the 9th month of the year in the Julian and Gregorian Calendars and one of four months with a length of 30 days.September in the Southern Hemisphere is the seasonal equivalent of March in the Northern Hemisphere....

 
29 30
October
October
October is the tenth month of the year in the Julian and Gregorian Calendars and one of seven months with a length of 31 days. The eighth month in the old Roman calendar, October retained its name after January and February were inserted into the calendar that had originally been created by the...

 
31 31
November
November
November is the 11th month of the year in the Julian and Gregorian Calendars and one of four months with the length of 30 days. November was the ninth month of the ancient Roman calendar...

 
29 30
December
December
December is the 12th and last month of the year in the Julian and Gregorian Calendars and one of seven months with the length of 31 days.December starts on the same day as September every year and ends on the same day as April every year.-Etymology:...

 
29 31
Mercedonius/Intercalaris
Mercedonius
Mercedonius, also known as Intercalaris, was the intercalary month added in leap years of the Roman calendar. The resulting year was either 377 or 378 days long. The exact mechanism by which this was done is not clearly specified in ancient sources. Modern scholarship holds that Februarius was...

 
0 (leap years: 27)
(inserted between the shortened
February and March)
(abolished)

Motivation


The ordinary year in the previous Roman calendar consisted of 12 months, for a total of 355 days. In addition, a 27-day intercalary month, the Mensis Intercalaris
Mercedonius
Mercedonius, also known as Intercalaris, was the intercalary month added in leap years of the Roman calendar. The resulting year was either 377 or 378 days long. The exact mechanism by which this was done is not clearly specified in ancient sources. Modern scholarship holds that Februarius was...

, was sometimes inserted between February and March. This intercalary month was formed by inserting 22 days after the first 23 or 24 days of February; the last five days of February, which counted down toward the start of March, become the last five days of Intercalaris. The net effect was to add 22 or 23 days to the year, forming an intercalary year of 377 or 378 days.

According to the later writers Censorinus
Censorinus
Censorinus, Roman grammarian and miscellaneous writer, flourished during the 3rd century AD.He was the author of a lost work De Accentibus and of an extant treatise De Die Natali, written in 238, and dedicated to his patron Quintus Caerellius as a birthday gift...

 and Macrobius, the ideal intercalary cycle consisted of ordinary years of 355 days alternating with intercalary years, alternately 377 and 378 days long. On this system, the average Roman year would have had 366¼ days over four years, giving it an average drift of one day per year relative to any solstice
Solstice
A solstice is an astronomical event that happens twice each year when the Sun's apparent position in the sky, as viewed from Earth, reaches its northernmost or southernmost extremes...

 or equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...

. Macrobius describes a further refinement wherein, for 8 years out of 24, there were only three intercalary years, each of 377 days. This refinement averages the length of the year to 365¼ days over 24 years. In practice, intercalations did not occur schematically according to these ideal systems, but were determined by the pontifices
Pontifex Maximus
The Pontifex Maximus was the high priest of the College of Pontiffs in ancient Rome. This was the most important position in the ancient Roman religion, open only to patricians until 254 BC, when a plebeian first occupied this post...

. So far as can be determined from the historical evidence, they were much less regular than these ideal schemes suggest. They usually occurred every second or third year, but were sometimes omitted for much longer, and occasionally occurred in two consecutive years.

If managed correctly this system allowed the Roman year, on average, to stay roughly aligned to a tropical year. However, since the Pontifices were often politicians, and because a Roman magistrate's term of office
Official
An official is someone who holds an office in an organization or government and participates in the exercise of authority .A government official or functionary is an official who is involved in public...

 corresponded with a calendar year, this power was prone to abuse: a Pontifex could lengthen a year in which he or one of his political allies was in office, or refuse to lengthen one in which his opponents were in power.
If too many intercalations were omitted, as happened after the Second Punic War
Second Punic War
The Second Punic War, also referred to as The Hannibalic War and The War Against Hannibal, lasted from 218 to 201 BC and involved combatants in the western and eastern Mediterranean. This was the second major war between Carthage and the Roman Republic, with the participation of the Berbers on...

 and during the Civil Wars
Roman civil wars
There were several Roman civil wars, especially during the late Republic. The most famous of these are the war in the 40s BC between Julius Caesar and the optimate faction of the senatorial elite initially led by Pompey and the subsequent war between Caesar's successors, Octavian and Mark Antony in...

, the calendar would drift rapidly out of alignment with the tropical year. Moreover, because intercalations were often determined quite late, the average Roman citizen often did not know the date, particularly if he were some distance from the city. For these reasons, the last years of the pre-Julian calendar were later known as "years of confusion". The problems became particularly acute during the years of Julius Caesar's pontificate before the reform, 63–46 BC, when there were only five intercalary months, whereas there should have been eight, and none at all during the five Roman years before 46 BC. For example, Caesar crossed the Rubicon
Rubicon
The Rubicon is a shallow river in northeastern Italy, about 80 kilometres long, running from the Apennine Mountains to the Adriatic Sea through the southern Emilia-Romagna region, between the towns of Rimini and Cesena. The Latin word rubico comes from the adjective "rubeus", meaning "red"...

 on January 10, 49 BC of the official calendar, but the official calendar had drifted so far away from the seasons that it was actually mid-autumn.

The reform was intended to correct this problem permanently, by creating a calendar that remained aligned to the sun without any human intervention. This feature proved useful very soon after the new calendar came into effect. Varro
Varro
Varro was a Roman cognomen carried by:*Marcus Terentius Varro, sometimes known as Varro Reatinus, the scholar*Publius Terentius Varro or Varro Atacinus, the poet*Gaius Terentius Varro, the consul defeated at the battle of Cannae...

 used it in 37 BC to fix calendar dates for the start of the four seasons, which would have been impossible only 8 years earlier. A century later, when Pliny
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...

 gave the dates (established by Caesar) of some natural and astronomical phenomena along the year, such as the dates of the solstices and the equinoxes (the 8th day before the calends of January, April, July and October (25 December, 25 March, 24 June, 24 September, respectively)), this stability had become an ordinary fact of life.

Context of the reform


The approximation of 365¼ days for the tropical year had been known for a long time but was not used directly since ancient calendars were not solar (except in Egypt). It was the mean length of the year in the octaeteris
Octaeteris
In astronomy, an octaeteris is the period of eight solar years after which the moon phase occurs on the same day of the year plus one or two days....

, a cycle of 8 lunar years popularized by Cleostratus
Cleostratus
Cleostratus was an astronomer of ancient Greece. He was a native of Tenedos, and the Chaldean astronomer Naburimannu may have been a contemporary of him. He is believed by some scholars to have introduced the zodiac and the solar calendar to Greece from Babylonia. Censorinus Cleostratus (ca....

 (and also commonly attributed to Eudoxus
Eudoxus
Eudoxus or Eudoxos was the name of two ancient Greeks:* Eudoxus of Cnidus , Greek astronomer and mathematician.* Eudoxus of Cyzicus , Greek navigator....

) which was used in some early Greek calendars, notably in Athens
Attic calendar
The Attic calendar is a hellenic calendar that was in use in ancient Attica, the ancestral territory of the Athenian polis. This article focuses on the 5th and 4th centuries BC, the classical period that produced some of the most significant works of ancient Greek literature. Because of the...

. The same value was the basis of the 76 years cycle
Callippic cycle
In astronomy and calendar studies, the Callippic cycle is a particular approximate common multiple of the year and the synodic month, that was proposed by Callippus in 330 BC...

 devised by Callippus
Callippus
Callippus or Calippus was a Greek astronomer and mathematician.Callippus was born at Cyzicus, and studied under Eudoxus of Cnidus at the Academy of Plato. He also worked with Aristotle at the Lyceum, which means that he was active in Athens prior to Aristotle's death in 322...

 (a student under Eudoxus) to improve the Metonic cycle. The length of the year in the cycle of Meton
Metonic cycle
In astronomy and calendar studies, the Metonic cycle or Enneadecaeteris is a period of very close to 19 years which is remarkable for being very nearly a common multiple of the solar year and the synodic month...

 was less accurate: about 30 minutes too long (1 day in 48 years).

In Egypt, a fixed year
Egyptian calendar
The ancient civil Egyptian calendar had a year that was 360 days long and was divided into 12 months of 30 days each, plus five extra days at the end of the year. The months were divided into three weeks of ten days each...

 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
Decree of Canopus
The Decree of Canopus is a bilingual inscription in two languages, and in three scripts. It was written in three writing systems: Egyptian hieroglyphs, Egyptian Demotic, and Greek, on an ancient Egyptian memorial stone stele, the Stone of Canopus...

). Caesar probably experienced the solar calendar in that country. He landed in the Nile delta in October 48 BC and soon became embroiled in the Ptolemaic dynastic war, especially when Cleopatra managed to be "introduced" to him in Alexandria
Alexandria
Alexandria is the second-largest city of Egypt, with a population of 4.1 million, extending about along the coast of the Mediterranean Sea in the north central part of the country; it is also the largest city lying directly on the Mediterranean coast. It is Egypt's largest seaport, serving...

. Caesar imposed a peace, and a banquet was held to celebrate the event. Lucan
Lucan
Lucan is the common English name of the Roman poet Marcus Annaeus Lucanus.Lucan may also refer to:-People:*Arthur Lucan , English actor*Sir Lucan the Butler, Knight of the Round Table in Arthurian legend...

 depicted Caesar talking to a wise man called Acoreus
Acoreus
Acoreus was a wise man consulted by Julius Caesar, according to the Roman writer Lucan, asking him many questions about ancient Egypt’s history and its calendar...

 during the feast, stating his intention to create a calendar more perfect than that of Eudoxus (Eudoxus was popularly credited with having determined the length of the year to be 365¼ days). 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.

Caesar returned to Rome in 46 BC and, according to Plutarch
Plutarch
Plutarch then named, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. 46 – 120 AD, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...

, called in the best philosophers and mathematicians of his time to solve the problem of the calendar. Pliny
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...

 says that Caesar was aided in his reform by the astronomer Sosigenes of Alexandria
Sosigenes of Alexandria
Sosigenes of Alexandria was named by Pliny the Elder as the astronomer consulted by Julius Caesar for the design of the Julian calendar. Little is known about him apart from Pliny's Natural History...

 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. 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 365¼ days of the Greek astronomy. According to Macrobius, Caesar was assisted in this by a certain Marcus Flavius.

Julian reform


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 (708 AUC) 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 African campaign in late Quintilis (July), he added 67 (= 22 + 23 + 22) more days by inserting two extraordinary intercalary months between November and December. 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 "Unodecember
Undecimber
Undecimber or Undecember is a name for a thirteenth month in a calendar that normally has twelve months. Duodecember is similarly a fourteenth month.-Latin:...

" and "Duodecember". Their individual lengths are unknown, as is the position of the Nones and Ides within them. 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 first year of operation of the new calendar was 45 BC.

A passage in Macrobius has been interpreted 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. However, more recent studies of the manuscripts have shown that the word on which this is based, which was formerly read as lunam, should be read as linam, meaning that Macrobius was simply stating that Caesar published an edict giving the revised calendar.

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 Ianuarius, Sextilis (later changed in name to Augustus) and December, and one extra day was added to Aprilis, Iunius, September and November. Februarius 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. (See Debunked month length myths below for stories purporting otherwise).

Macrobius states that the extra days were added immediately before the last day of each month to avoid disturbing the position of the established Roman fasti (days prescribed for certain events) relative to the start of the month. However, since Roman dates after the Ides of the month counted down toward the start of the next month, the extra days had the effect of raising the initial value of the count of the day after the Ides. Romans of the time born after the Ides of a month responded differently to the effect of this change on their birthdays. Mark Antony
Mark Antony
Marcus Antonius , known in English as Mark Antony, was a Roman politician and general. As a military commander and administrator, he was an important supporter and loyal friend of his mother's cousin Julius Caesar...

 kept his birthday on the 14th day of Ianuarius, which changed its date from a.d. XVII Kal. Feb. to a.d. XIX Kal. Feb., a date that had previously not existed. Livia
Livia
Livia Drusilla, , after her formal adoption into the Julian family in AD 14 also known as Julia Augusta, was a Roman empress as the third wife of the Emperor Augustus and his adviser...

 kept the date of her birthday unchanged at a.d. III Kal. Feb., which moved it from the 28th to the 30th day of Ianuarius, a day that had previously not existed. Augustus
Augustus
Augustus ;23 September 63 BC – 19 August AD 14) is considered the first emperor of the Roman Empire, which he ruled alone from 27 BC until his death in 14 AD.The dates of his rule are contemporary dates; Augustus lived under two calendars, the Roman Republican until 45 BC, and the Julian...

 kept his on the 23rd day of September, but both the old date (a.d. VIII Kal. Oct.) and the new (a.d. IX Kal. Oct.) were celebrated in some places.

The old intercalary month was abolished. The new leap day was dated as ante diem bis sextum Kalendas Martias, 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 1st century jurist Celsus
Publius Iuventius Celsus
Publius Iuventius Celsus Titus Aufidius Hoenius Severianus – the son of a little-known jurist of the same name, hence also Celsus filius – was, together with Julian, the most influential ancient Roman jurist of the High Classical era....

, 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 Ideler
Christian Ludwig Ideler
Christian Ludwig Ideler , German chronologist and astronomer, was born near Perleberg on the 21st of September 1766.-Life:...

 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 Mommsen
Theodor Mommsen
Christian Matthias Theodor Mommsen was a German classical scholar, historian, jurist, journalist, politician, archaeologist, and writer generally regarded as the greatest classicist of the 19th century. His work regarding Roman history is still of fundamental importance for contemporary research...

, 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.

There is no doubt that the bissextile day eventually became the earlier of the two days. In 238 Censorinus
Censorinus
Censorinus, Roman grammarian and miscellaneous writer, flourished during the 3rd century AD.He was the author of a lost work De Accentibus and of an extant treatise De Die Natali, written in 238, and dedicated to his patron Quintus Caerellius as a birthday gift...

 stated that it was inserted after the 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 the 24th to 28th days of February in a common year and the 25th to the 29th days 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
Bede
Bede , also referred to as Saint Bede or the Venerable Bede , was a monk at the Northumbrian monastery of Saint Peter at Monkwearmouth, today part of Sunderland, England, and of its companion monastery, Saint Paul's, in modern Jarrow , both in the Kingdom of Northumbria...

 in 725, and other medieval computists
Computus
Computus is the calculation of the date of Easter in the Christian calendar. The name has been used for this procedure since the early Middle Ages, as it was one of the most important computations of the age....

 (calculators of Easter
Easter
Easter is the central feast in the Christian liturgical year. According to the Canonical gospels, Jesus rose from the dead on the third day after his crucifixion. His resurrection is celebrated on Easter Day or Easter Sunday...

) followed this rule, as did the liturgical calendar
Liturgical year
The liturgical year, also known as the church year, consists of the cycle of liturgical seasons in Christian churches which determines when feast days, including celebrations of saints, are to be observed, and which portions of Scripture are to be read. Distinct liturgical colours may appear in...

 of the Roman Catholic Church until 1970.

During the late Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

 days in the month came to be numbered in consecutive day order. Consequently, the leap day was considered to be the last day in February in leap years, i.e. 29 February, which is its current position.

Leap year error


Although the new calendar was much simpler than the pre-Julian calendar, the pontifices apparently misunderstood the algorithm for leap years. They added a leap day every three years, instead of every four years. According to Macrobius, the error was the result of counting inclusively, so that the four-year cycle was considered as including both the first and fourth years; perhaps the earliest recorded example of a fence post error. After 36 years, this resulted in three too many leap days. Augustus
Augustus
Augustus ;23 September 63 BC – 19 August AD 14) is considered the first emperor of the Roman Empire, which he ruled alone from 27 BC until his death in 14 AD.The dates of his rule are contemporary dates; Augustus lived under two calendars, the Roman Republican until 45 BC, and the Julian...

 remedied this discrepancy by restoring the correct frequency. He also skipped three leap days in order to realign the year. Once this reform was complete—after AD 8 at the latest—the Roman calendar was the same as the Julian proleptic calendar.

The historic sequence of leap years in this period is not given explicitly by any ancient source, although the existence of the triennial leap year cycle is confirmed by an inscription that dates from 9 or 8 BC. The chronologist
Chronology
Chronology is the science of arranging events in their order of occurrence in time, such as the use of a timeline or sequence of events. It is also "the determination of the actual temporal sequence of past events".Chronology is part of periodization...

 Joseph Scaliger established in 1583 that the Augustan reform was instituted in 8 BC, and inferred that the sequence of leap years was 42, 39, 36, 33, 30, 27, 24, 21, 18, 15, 12, 9 BC, AD 8, 12 etc. This proposal is still the most widely accepted solution, although Ideler and Mommsen
Theodor Mommsen
Christian Matthias Theodor Mommsen was a German classical scholar, historian, jurist, journalist, politician, archaeologist, and writer generally regarded as the greatest classicist of the 19th century. His work regarding Roman history is still of fundamental importance for contemporary research...

, among others, argued that there was an additional bissextile day in the first year of the Julian reform, i.e. that 45 BC was also a leap year.

Around the time Scaliger's proposal was published, several other solutions were suggested on the same data. In 1590, Bunting
Heinrich Bünting
Heinrich Bünting was a Protestant pastor and theologian. He is best known for his book of woodcut maps titled Itinerarium Sacrae Scripturae first published in 1581.-Life:...

 proposed the sequence 45, 42, 39, 36, 33, 30, 27, 24, 21, 18, 15, 12 BC, AD 4, 8, 12 etc. This solution assumed the same phase for the triennial cycle as Scaliger, but differed on the date of its start (45 vs 42 BC) and end (12 vs 9 BC) and on the date at which the correct cycle was resumed (AD 4 vs 8). Other scholars proposed a different phase. Also in 1590, Christmann
Jakob Christmann
Jakob Christmann was a German Orientalist who also studied problems of astronomy.- Life :...

 published an influential translation of Alfraganus, which argued that Caesar had intended leap years to fall in every fourth reformed year, i.e. in 42, 38..., suggesting a triennial cycle of 43, 40, 37, 34, 31, 28, 25, 22, 19, 16, 13, 10 BC. Through an arithmetical error in interpreting years of the Julian reform, he supposed that the correct cycle had resumed in AD 7, but other scholars followed the same line of argument while correcting for this. Harriot
Thomas Harriot
Thomas Harriot was an English astronomer, mathematician, ethnographer, and translator. Some sources give his surname as Harriott or Hariot or Heriot. He is sometimes credited with the introduction of the potato to Great Britain and Ireland...

 considered the sequence 43, 40, 37, 34, 31, 28, 25, 22, 19, 16, 13, 10 BC, AD 4, 8, 12 etc., while in 1614 Kepler
Johannes Kepler
Johannes Kepler was a German mathematician, astronomer and astrologer. A key figure in the 17th century scientific revolution, he is best known for his eponymous laws of planetary motion, codified by later astronomers, based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican...

 discussed 43, 40, 37, 34, 31, 28, 25, 22, 19, 16, 13, 10 BC, AD 8, 12 etc. However Scaliger's solution became generally adopted.

Other solutions have occasionally been proposed since the 17th century. In 1883 the German chronologist Matzat proposed 44, 41, 38, 35, 32, 29, 26, 23, 20, 17, 14, 11 BC, AD 4, 8, 12 etc., based on a passage in Dio Cassius
Dio Cassius
Lucius Cassius Dio Cocceianus , known in English as Cassius Dio, Dio Cassius, or Dio was a Roman consul and a noted historian writing in Greek...

 that mentions a leap day in 41 BC that was said to be contrary to (Caesar's) rule. In 1889, Soltau suggested a modified version of this: 45, 41, 38, 35, 32, 29, 26, 23, 20, 17, 14, 11 BC, AD 8, 12 etc. In the 1960s Radke argued the reform was actually instituted when Augustus became pontifex maximus in 12 BC, suggesting the sequence 45, 42, 39, 36, 33, 30, 27, 24, 21, 18, 15, 12 BC, AD 4, 8, 12 etc., the same solution which Bunting had proposed in 1590.

With the solutions of Scaliger, Kepler and Soltau, the Roman calendar was not finally aligned to the Julian calendar of later times until 25 February (a.d. V Kal. Mar.) AD 4. On Bunting's, Harriot's, Matzat's and Radke's solutions, the two calendars were aligned on 25 February 1 BC.

In 1999, an Egyptian papyrus
Papyrus
Papyrus is a thick paper-like material produced from the pith of the papyrus plant, Cyperus papyrus, a wetland sedge that was once abundant in the Nile Delta of Egypt....

 was published that gives an ephemeris
Ephemeris
An ephemeris is a table of values that gives the positions of astronomical objects in the sky at a given time or times. Different kinds of ephemerides are used for astronomy and astrology...

 table for 24 BC with both Roman and Egyptian dates. While the Roman dates match the proleptic Julian calendar
Proleptic Julian calendar
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...

, they are not aligned with any previously proposed solution for the triennial cycle. One suggested resolution of this problem, which matches the data of the papyrus, is a new triennial sequence: 44, 41, 38, 35, 32, 29, 26, 23, 20, 17, 14, 11, 8 BC, AD 4, 8, 12 etc. This sequence is very close to that proposed by Matzat, differing only in the date of the last triennial leap year. On it, the three excess leap days added during the years that the triennial cycle was in operation were backed out on the triennial cycle (5, 2 BC, AD 2), not the quadrennial cycle (5, 1 BC, AD 4 (Scaliger) or 8, 4 BC, AD 1 (Matzat)); the standard Julian leap year sequence began in AD 4, the 12th year of the Augustan reform; and the Roman calendar was finally aligned to the Julian calendar in 1 BC (with AD 1 the first full year of alignment).

Month names


Immediately after the Julian reform, the twelve months of the Roman calendar were named Ianuarius, Februarius, Martius, Aprilis, Maius, Iunius, Quintilis, Sextilis, September, October, November, and December, just as they were before the reform. The old intercalary month, the Mensis Intercalaris
Mercedonius
Mercedonius, also known as Intercalaris, was the intercalary month added in leap years of the Roman calendar. The resulting year was either 377 or 378 days long. The exact mechanism by which this was done is not clearly specified in ancient sources. Modern scholarship holds that Februarius was...

, was abolished and replaced with a single intercalary day at the same point (i.e. five days before the end of Februarius). The first month of the year continued to be Ianuarius, as it had been since 153 BC.

The Romans later renamed months after Julius Caesar
Julius Caesar
Gaius Julius Caesar was a Roman general and statesman and a distinguished writer of Latin prose. He played a critical role in the gradual transformation of the Roman Republic into the Roman Empire....

 and Augustus
Augustus
Augustus ;23 September 63 BC – 19 August AD 14) is considered the first emperor of the Roman Empire, which he ruled alone from 27 BC until his death in 14 AD.The dates of his rule are contemporary dates; Augustus lived under two calendars, the Roman Republican until 45 BC, and the Julian...

, renaming Quintilis (originally, "the fifth month", with March = month 1) as Iulius (July) in 44 BC and Sextilis ("sixth month") as Augustus (August) in 8 BC. Quintilis was renamed to honour Caesar because it was the month of his birth. According to a senatus consultum quoted by Macrobius, Sextilis was renamed to honour Augustus because several of the most significant events in his rise to power, culminating in the fall of Alexandria, occurred in that month.

Other months were renamed by other emperors, but apparently none of the later changes survived their deaths. Caligula
Caligula
Caligula , also known as Gaius, was Roman Emperor from 37 AD to 41 AD. Caligula was a member of the house of rulers conventionally known as the Julio-Claudian dynasty. Caligula's father Germanicus, the nephew and adopted son of Emperor Tiberius, was a very successful general and one of Rome's most...

 renamed September ("seventh month") as Germanicus
Germanicus
Germanicus Julius Caesar , commonly known as Germanicus, was a member of the Julio-Claudian dynasty and a prominent general of the early Roman Empire. He was born in Rome, Italia, and was named either Nero Claudius Drusus after his father or Tiberius Claudius Nero after his uncle...

; Nero
Nero
Nero , was Roman Emperor from 54 to 68, and the last in the Julio-Claudian dynasty. Nero was adopted by his great-uncle Claudius to become his heir and successor, and succeeded to the throne in 54 following Claudius' death....

 renamed Aprilis (April) as Neroneus, Maius (May) as Claudius and Iunius (June) as Germanicus; and Domitian
Domitian
Domitian was Roman Emperor from 81 to 96. Domitian was the third and last emperor of the Flavian dynasty.Domitian's youth and early career were largely spent in the shadow of his brother Titus, who gained military renown during the First Jewish-Roman War...

 renamed September as Germanicus
Germanicus
Germanicus Julius Caesar , commonly known as Germanicus, was a member of the Julio-Claudian dynasty and a prominent general of the early Roman Empire. He was born in Rome, Italia, and was named either Nero Claudius Drusus after his father or Tiberius Claudius Nero after his uncle...

 and October ("eighth month") as Domitianus. At other times, September was also renamed as Antoninus
Antoninus Pius
Antoninus Pius , also known as Antoninus, was Roman Emperor from 138 to 161. He was a member of the Nerva-Antonine dynasty and the Aurelii. He did not possess the sobriquet "Pius" until after his accession to the throne...

 and Tacitus
Marcus Claudius Tacitus
Tacitus , was Roman Emperor from 275 to 276. During his short reign he campaigned against the Goths and the Heruli, for which he received the title Gothicus Maximus.-Biography:Tacitus was born in Interamna , in Italia...

, and November ("ninth month") was renamed as Faustina
Faustina the Elder
Annia Galeria Faustina, more familiarly referred to as Faustina I , was a Roman Empress and wife of Roman Emperor Antoninus Pius.-Early life:...

 and Romanus. Commodus
Commodus
Commodus , was Roman Emperor from 180 to 192. He also ruled as co-emperor with his father Marcus Aurelius from 177 until his father's death in 180. His name changed throughout his reign; see changes of name for earlier and later forms. His accession as emperor was the first time a son had succeeded...

 was unique in renaming all twelve months after his own adopted names (January to December): Amazonius, Invictus, Felix, Pius, Lucius, Aelius, Aurelius, Commodus, Augustus, Herculeus, Romanus, and Exsuperatorius.

Much more lasting than the ephemeral month names of the post-Augustan Roman emperors were the names introduced by Charlemagne
Charlemagne
Charlemagne was King of the Franks from 768 and Emperor of the Romans from 800 to his death in 814. He expanded the Frankish kingdom into an empire that incorporated much of Western and Central Europe. During his reign, he conquered Italy and was crowned by Pope Leo III on 25 December 800...

. He renamed all of the months agriculturally into Old High German
Old High German
The term Old High German refers to the earliest stage of the German language and it conventionally covers the period from around 500 to 1050. Coherent written texts do not appear until the second half of the 8th century, and some treat the period before 750 as 'prehistoric' and date the start of...

. They were used until the 15th century, over 700 years after his rule, and continued with some modifications until the late 18th century in Germany and in the Netherlands. The names (January to December) were: Wintarmanoth (winter month), Hornung (the month when the male red deer sheds its antlers), Lentzinmanoth (Lent month), Ostarmanoth (Easter month), Wonnemanoth (love-making month), Brachmanoth (plowing month), Heuvimanoth (hay month), Aranmanoth (harvest month), Witumanoth (wood month), Windumemanoth (vintage month), Herbistmanoth (autumn/harvest month), and Heilagmanoth (holy month).

The original Roman names as fixed in 8 BC are still in use in North Africa, where Berber farmers use the Julian calendar in everyday life. They are pronounced today Yennair, Febrair, Mars, Ibril, Mai, Yuniu, Yulius, Ghusht, Shutambir, Ktuber, Nuwambir, Dujanbir, with local variations; they are also used often in classic Arabic and medieval Arabic texts when referring to the months of the solar 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 4th century documents were also being dated according to the 15-year cycle of the indiction
Indiction
An indiction is any of the years in a 15-year cycle used to date medieval documents throughout Europe, both East and West. Each year of a cycle was numbered: first indiction, second indiction, etc...

. In 537, Justinian
Justinian I
Justinian I ; , ; 483– 13 or 14 November 565), commonly known as Justinian the Great, was Byzantine Emperor from 527 to 565. During his reign, Justinian sought to revive the Empire's greatness and reconquer the lost western half of the classical Roman Empire.One of the most important figures of...

 required that henceforth the date must include the name of the emperor and his regnal year, in addition to the indiction
Indiction
An indiction is any of the years in a 15-year cycle used to date medieval documents throughout Europe, both East and West. Each year of a cycle was numbered: first indiction, second indiction, etc...

 and the consul, while also allowing the use of local eras.

In 309 and 310, and from time to time thereafter, no consuls were appointed. When this happened, the consular date was given a count of years since the last consul (so-called "post-consular" dating). After 541, only the reigning emperor held the consulate, typically for only one year in his reign, and so post-consular dating became the norm. Similar post-consular dates were also known in the West in the early 6th century. The system of consular dating, long obsolete, was formally abolished in the law code of Leo VI
Leo VI the Wise
Leo VI, surnamed the Wise or the Philosopher , was Byzantine emperor from 886 to 912. The second ruler of the Macedonian dynasty , he was very well-read, leading to his surname...

, issued in 888.

Only rarely did the Romans number the year from the founding of the city (of Rome)
Founding of Rome
The founding of Rome is reported by many legends, which in recent times are beginning to be supplemented by scientific reconstructions.- Development of the city :...

, ab urbe condita
Ab urbe condita
Ab urbe condita is Latin for "from the founding of the City ", traditionally set in 753 BC. AUC is a year-numbering system used by some ancient Roman historians to identify particular Roman years...

(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
Fasti
In ancient Rome, the fasti were chronological or calendar-based lists, or other diachronic records or plans of official and religiously sanctioned events...

, an inscription containing an official list of the consuls which was published by Augustus, used an epoch
Epoch (reference date)
In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...

 of 752 BC. The epoch used by Varro
Marcus Terentius Varro
Marcus Terentius Varro was an ancient Roman scholar and writer. He is sometimes called Varro Reatinus to distinguish him from his younger contemporary Varro Atacinus.-Biography:...

, 753 BC, has been adopted by modern historians. Indeed, Renaissance
Renaissance
The Renaissance was a cultural movement that spanned roughly the 14th to the 17th century, beginning in Italy in the Late Middle Ages and later spreading to the rest of Europe. The term is also used more loosely to refer to the historical era, but since the changes of the Renaissance were not...

 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
Censorinus
Censorinus, Roman grammarian and miscellaneous writer, flourished during the 3rd century AD.He was the author of a lost work De Accentibus and of an extant treatise De Die Natali, written in 238, and dedicated to his patron Quintus Caerellius as a birthday gift...

, writing in the 3rd century AD, states that, in his time, the AUC year began with the Parilia
Parilia
thumb|250px|Festa di Pales, o L'estate , a reimagining of the Festival of Pales by [[Joseph-Benoît Suvée]]In ancient Roman religion, the Parilia is an agricultural festival performed annually on April 21, aimed at cleansing both sheep and shepherd. It is carried out in acknowledgment to the Roman...

, 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
Lent
In the Christian tradition, Lent is the period of the liturgical year from Ash Wednesday to Easter. The traditional purpose of Lent is the preparation of the believer – through prayer, repentance, almsgiving and self-denial – for the annual commemoration during Holy Week of the Death and...

, which was observed until the Saturday before Easter Sunday, the early Roman church did not celebrate Easter after 21 April.

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
Augustus
Augustus ;23 September 63 BC – 19 August AD 14) is considered the first emperor of the Roman Empire, which he ruled alone from 27 BC until his death in 14 AD.The dates of his rule are contemporary dates; Augustus lived under two calendars, the Roman Republican until 45 BC, and the Julian...

. This led to the adoption of several local eras for the Julian calendar, such as the Era of Actium and the Spanish Era
Spanish era
The Spanish era, Hispanic era or Caesar era refers to the dating system used in Hispania until the 14th century, when the Anno Domini system was adopted. It began with year one in what is 38 BC, probably the date of a new tax imposed by the Roman Republic on the subdued population of Iberia....

, some of which were used for a considerable time. Perhaps the best known is the Era of Martyrs
Era of Martyrs
The Era of the Martyrs , also known as the Diocletian era , is a method of numbering years used by the Church of Alexandria beginning in the 4th century anno Domini and by the Coptic Orthodox Church of Alexandria from the 5th century to the present. Western Christians were aware of it but did not...

, sometimes also called Anno Diocletiani (after Diocletian
Diocletian
Diocletian |latinized]] upon his accession to Diocletian . c. 22 December 244  – 3 December 311), was a Roman Emperor from 284 to 305....

), which was often used by the Alexandrian Christians
Alexandria
Alexandria is the second-largest city of Egypt, with a population of 4.1 million, extending about along the coast of the Mediterranean Sea in the north central part of the country; it is also the largest city lying directly on the Mediterranean coast. It is Egypt's largest seaport, serving...

 to number their Easters during the 4th and 5th centuries, and continues to be used by the Coptic and Ethiopian churches, as well as influencing the modern Ethiopian calendar
Ethiopian calendar
The Ethiopian calendar , also called the Ge'ez calendar, is the principal calendar used in Ethiopia and also serves as the liturgical calendar for Christians in Eritrea belonging to the Eritrean Orthodox Church, Eastern Catholic Church and Lutheran Evangelical Church of Eritrea...

.

In the Eastern Mediterranean, the efforts of Christian chronographers such as Annianus of Alexandria
Annianus of Alexandria
Annianus of Alexandria or Annianos was a monk who flourished in Alexandria during the bishopric of Theophilus of Alexandria around the beginning of the fifth century...

 to date the Biblical creation of the world led to the introduction of Anno Mundi
Anno Mundi
' , abbreviated as AM or A.M., refers to a Calendar era based on the Biblical creation of the world. Numerous efforts have been made to determine the Biblical date of Creation, yielding varying results. Besides differences in interpretation, which version of the Bible is being referenced also...

 eras based on this event. The most important of these was the Etos Kosmou, used throughout the Byzantine world from the 10th century and in Russia until 1700. In the West, Dionysius Exiguus
Dionysius Exiguus
Dionysius Exiguus was a 6th-century monk born in Scythia Minor, modern Dobruja shared by Romania and Bulgaria. He was a member of the Scythian monks community concentrated in Tomis, the major city of Scythia Minor...

 proposed the system of Anno Domini
Anno Domini
and Before Christ are designations used to label or number years used with the Julian and Gregorian calendars....

 in 525. This era gradually spread through the western Christian world, once the system was adopted by Bede
Bede
Bede , also referred to as Saint Bede or the Venerable Bede , was a monk at the Northumbrian monastery of Saint Peter at Monkwearmouth, today part of Sunderland, England, and of its companion monastery, Saint Paul's, in modern Jarrow , both in the Kingdom of Northumbria...

.

New Year's Day


The Roman calendar began the year on 1 January, and this remained the start of the year after the Julian reform. However, even after local calendars were aligned to the Julian calendar, they started the new year on different dates. The Alexandrian calendar in Egypt started on 29 August (30 August after an Alexandrian leap year). Several local provincial calendars were aligned to start on the birthday of Augustus, 23 September. The indiction
Indiction
An indiction is any of the years in a 15-year cycle used to date medieval documents throughout Europe, both East and West. Each year of a cycle was numbered: first indiction, second indiction, etc...

 caused the Byzantine
Byzantine Empire
The Byzantine Empire was the Eastern Roman Empire during the periods of Late Antiquity and the Middle Ages, centred on the capital of Constantinople. Known simply as the Roman Empire or Romania to its inhabitants and neighbours, the Empire was the direct continuation of the Ancient Roman State...

 year, which used the Julian calendar, to begin on :1 September; this date is still used in the Eastern Orthodox Church
Eastern Orthodox Church
The Orthodox Church, officially called the Orthodox Catholic Church and commonly referred to as the Eastern Orthodox Church, is the second largest Christian denomination in the world, with an estimated 300 million adherents mainly in the countries of Belarus, Bulgaria, Cyprus, Georgia, Greece,...

 for the beginning of the liturgical year
Liturgical year
The liturgical year, also known as the church year, consists of the cycle of liturgical seasons in Christian churches which determines when feast days, including celebrations of saints, are to be observed, and which portions of Scripture are to be read. Distinct liturgical colours may appear in...

. When the Julian calendar was adopted in AD 988 by Vladimir I of Kiev
Vladimir I of Kiev
Vladimir Sviatoslavich the Great Old East Slavic: Володимѣръ Свѧтославичь Old Norse as Valdamarr Sveinaldsson, , Vladimir, , Volodymyr, was a grand prince of Kiev, ruler of Kievan Rus' in .Vladimir's father was the prince Sviatoslav of the Rurik dynasty...

, the year was numbered Anno Mundi
Anno Mundi
' , abbreviated as AM or A.M., refers to a Calendar era based on the Biblical creation of the world. Numerous efforts have been made to determine the Biblical date of Creation, yielding varying results. Besides differences in interpretation, which version of the Bible is being referenced also...

 6496, beginning on 1 March, six months after the start of the Byzantine Anno Mundi year with the same number. In 1492 (AM 7000), Ivan III, according to church tradition, realigned the start of the year to 1 September, so that AM 7000 only lasted for six months in Russia, from 1 March to 31 August 1492.

During the Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

 1 January retained the name New Year's Day
New Year's Day
New Year's Day is observed on January 1, the first day of the year on the modern Gregorian calendar as well as the Julian calendar used in ancient Rome...

(or an equivalent name) in all Western Europe
Western Europe
Western Europe is a loose term for the collection of countries in the western most region of the European continents, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a geographic entity—the region lying in the...

an countries (affiliated with the Roman Catholic Church
Roman Catholic Church
The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with over a billion members. Led by the Pope, it defines its mission as spreading the gospel of Jesus Christ, administering the sacraments and exercising charity...

), since the medieval calendar continued to display the months from January to December (in twelve columns containing 28 to 31 days each), just as the Romans had. However, most of those countries began their numbered year on 25 December (the Nativity of Jesus
Jesus
Jesus of Nazareth , commonly referred to as Jesus Christ or simply as Jesus or Christ, is the central figure of Christianity...

), 25 March (the Incarnation of Jesus
Annunciation
The Annunciation, also referred to as the Annunciation to the Blessed Virgin Mary or Annunciation of the Lord, is the Christian celebration of the announcement by the angel Gabriel to Virgin Mary, that she would conceive and become the mother of Jesus the Son of God. Gabriel told Mary to name her...

, approximating the vernal equinox), or even Easter
Easter
Easter is the central feast in the Christian liturgical year. According to the Canonical gospels, Jesus rose from the dead on the third day after his crucifixion. His resurrection is celebrated on Easter Day or Easter Sunday...

, as in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 (see the Liturgical year
Liturgical year
The liturgical year, also known as the church year, consists of the cycle of liturgical seasons in Christian churches which determines when feast days, including celebrations of saints, are to be observed, and which portions of Scripture are to be read. Distinct liturgical colours may appear in...

 article for more details).

In England, even before 1752, 1 January was sometimes treated as the start of the new year – for example by Pepys – while the "year starting 25th March was called the Civil or Legal Year". To reduce misunderstandings on the date, it was not uncommon in parish registers for a new year heading after 24 March, for example 1661, to have another heading at the end of the following December indicating "1661/62". This was to explain to the reader that the year was 1661 Old Style and 1662 New Style.

Most Western European countries shifted the first day of their numbered year to 1 January while they were still using the Julian calendar, before they adopted the Gregorian calendar, many during the 16th century. The following table shows the years in which various countries adopted 1 January as the start of the year. Eastern European countries, with populations showing allegiance to the Orthodox Church
Orthodoxy
The word orthodox, from Greek orthos + doxa , is generally used to mean the adherence to accepted norms, more specifically to creeds, especially in religion...

, began the year on 1 September from about 988.
Country Year starting
1 January
Adoption of
new calendar
Republic of Venice
Republic of Venice
The Republic of Venice or Venetian Republic was a state originating from the city of Venice in Northeastern Italy. It existed for over a millennium, from the late 7th century until 1797. It was formally known as the Most Serene Republic of Venice and is often referred to as La Serenissima, in...

 
1522 1582
Holy Roman Empire
Holy Roman Empire
The Holy Roman Empire was a realm that existed from 962 to 1806 in Central Europe.It was ruled by the Holy Roman Emperor. Its character changed during the Middle Ages and the Early Modern period, when the power of the emperor gradually weakened in favour of the princes...

1544 1582
Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

, Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

 
1556 1582
Prussia
Prussia
Prussia was a German kingdom and historic state originating out of the Duchy of Prussia and the Margraviate of Brandenburg. For centuries, the House of Hohenzollern ruled Prussia, successfully expanding its size by way of an unusually well-organized and effective army. Prussia shaped the history...

, Denmark/Norway
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

1559 1700
Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 
1559 1753
France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 
1564
Edict of Roussillon
The Edict of Roussillon was a 1564 edict decreeing that the year would begin on January 1 in France.During a trip to various parts of his kingdom, the King of France, Charles IX, found that depending on the diocese, the year began either at Christmas or on 25 March , on 1 March, or at Easter.In...

 
1582
Southern Netherlands
Southern Netherlands
Southern Netherlands were a part of the Low Countries controlled by Spain , Austria and annexed by France...

 
1576 1582
Lorraine
Lorraine (province)
The Duchy of Upper Lorraine was an historical duchy roughly corresponding with the present-day northeastern Lorraine region of France, including parts of modern Luxembourg and Germany. The main cities were Metz, Verdun, and the historic capital Nancy....

 
1579 1760
Holland, Zeeland
Zeeland
Zeeland , also called Zealand in English, is the westernmost province of the Netherlands. The province, located in the south-west of the country, consists of a number of islands and a strip bordering Belgium. Its capital is Middelburg. With a population of about 380,000, its area is about...

 
1583 1582
Dutch Republic
Dutch Republic
The Dutch Republic — officially known as the Republic of the Seven United Netherlands , the Republic of the United Netherlands, or the Republic of the Seven United Provinces — was a republic in Europe existing from 1581 to 1795, preceding the Batavian Republic and ultimately...

 except
Holland and Zeeland
Zeeland
Zeeland , also called Zealand in English, is the westernmost province of the Netherlands. The province, located in the south-west of the country, consists of a number of islands and a strip bordering Belgium. Its capital is Middelburg. With a population of about 380,000, its area is about...

 
1583 1700
Scotland
Kingdom of Scotland
The Kingdom of Scotland was a Sovereign state in North-West Europe that existed from 843 until 1707. It occupied the northern third of the island of Great Britain and shared a land border to the south with the Kingdom of England...

 
1600 1752
Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 
1700 1918
Tuscany
Grand Duchy of Tuscany
The Grand Duchy of Tuscany was a central Italian monarchy that existed, with interruptions, from 1569 to 1859, replacing the Duchy of Florence. The grand duchy's capital was Florence...

 
1721 1750
British Empire
British Empire
The British Empire comprised the dominions, colonies, protectorates, mandates and other territories ruled or administered by the United Kingdom. It originated with the overseas colonies and trading posts established by England in the late 16th and early 17th centuries. At its height, it was the...

 excluding Scotland
1752 1752
Serbia
Serbia
Serbia , officially the Republic of Serbia , is a landlocked country located at the crossroads of Central and Southeast Europe, covering the southern part of the Carpathian basin and the central part of the Balkans...

 
1804 1918

Debunked theory on month lengths


The Julian reform set the lengths of the months to their modern values. However, a 13th century scholar, Sacrobosco, proposed a different explanation for the lengths of Julian months which is still widely repeated but is certainly wrong. According to Sacrobosco, the original scheme for the months in the Julian calendar was very regular, alternately long and short. From January through December, the month lengths according to Sacrobosco for the Roman Republican calendar were:
30, 29, 30, 29, 30, 29, 30, 29, 30, 29, 30, 29.


He then thought that Julius Caesar added one day to every month except February, a total of 11 more days, giving the year 365 days. A leap day could now be added to the extra short February:
31, 29/30, 31, 30, 31, 30, 31, 30, 31, 30, 31, 30.


He then said Augustus changed this to:
31, 28/29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31


so that the length of Augustus would not be shorter than (and therefore inferior to) the length of Iulius, giving us the irregular month lengths which are still in use.

There is abundant evidence disproving this theory. First, a wall painting of a Roman calendar
Roman calendar
The Roman calendar changed its form several times in the time between the founding of Rome and the fall of the Roman Empire. This article generally discusses the early Roman or pre-Julian calendars...

 predating the Julian reform has survived, which confirms the literary accounts that the months were already irregular before Julius Caesar reformed them:
29, 28, 31, 29, 31, 29, 31, 29, 29, 31, 29, 29.


Also, the Julian reform did not change the dates of the Nones and Ides. In particular, the Ides were late (on the 15th rather than 13th) in March, May, July and October, showing that these months always had 31 days in the Roman calendar, whereas Sacrobosco's theory requires that March, May and July were originally 30 days long and that the length of October was changed from 29 to 30 days by Caesar and to 31 days by Augustus. Further, Sacrobosco's theory is explicitly contradicted by the 3rd and 5th century authors Censorinus
Censorinus
Censorinus, Roman grammarian and miscellaneous writer, flourished during the 3rd century AD.He was the author of a lost work De Accentibus and of an extant treatise De Die Natali, written in 238, and dedicated to his patron Quintus Caerellius as a birthday gift...

 and Macrobius, and it is inconsistent with seasonal lengths given by Varro, writing in 37 BC, before the Augustan reform, with the 31-day Sextilis given by the new Egyptian papyrus from 24 BC, and with the 28-day February shown in the Fasti Caeretani, which is dated before 12 BC.

From Julian to Gregorian



The Julian calendar was in general use in Europe and Northern Africa from the times of the Roman Empire
Roman Empire
The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....

 until 1582, when Pope Gregory XIII
Pope Gregory XIII
Pope Gregory XIII , born Ugo Boncompagni, was Pope from 1572 to 1585. He is best known for commissioning and being the namesake for the Gregorian calendar, which remains the internationally-accepted civil calendar to this date.-Youth:He was born the son of Cristoforo Boncompagni and wife Angela...

 promulgated the Gregorian calendar
Gregorian calendar
The Gregorian calendar, also known as the Western calendar, or Christian calendar, is the internationally accepted civil calendar. It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582, a papal bull known by its opening words Inter...

. Reform was required because too many leap days are added with respect to the astronomical seasons on the Julian scheme. On average, the astronomical solstice
Solstice
A solstice is an astronomical event that happens twice each year when the Sun's apparent position in the sky, as viewed from Earth, reaches its northernmost or southernmost extremes...

s and the equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...

es advance by about 11 minutes per year against the Julian year. As a result, the calculated date
Computus
Computus is the calculation of the date of Easter in the Christian calendar. The name has been used for this procedure since the early Middle Ages, as it was one of the most important computations of the age....

 of Easter
Easter
Easter is the central feast in the Christian liturgical year. According to the Canonical gospels, Jesus rose from the dead on the third day after his crucifixion. His resurrection is celebrated on Easter Day or Easter Sunday...

 gradually moved out of phase with the March equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...

. While Hipparchus
Hipparchus
Hipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...

 and presumably Sosigenes
Sosigenes
There were several historical figures called Sosigenes:*Sosigenes of Alexandria, an astronomer consulted by Julius Caesar for the design of the Julian calendar....

 were aware of the discrepancy, although not of its correct value, it was evidently felt to be of little importance at the time of the Julian reform. However, it accumulated significantly over time: the Julian calendar gained a day about every 134 years. By 1582, it was ten days out of alignment from where it supposedly was in 325 during the Council of Nicaea
First Council of Nicaea
The First Council of Nicaea was a council of Christian bishops convened in Nicaea in Bithynia by the Roman Emperor Constantine I in AD 325...

.

The Gregorian calendar was soon adopted by most Catholic countries (e.g. Spain, Portugal, Poland, most of Italy). Protestant countries followed later, and the countries of Eastern Europe adopted the "new calendar" even later. In the British Empire
British Empire
The British Empire comprised the dominions, colonies, protectorates, mandates and other territories ruled or administered by the United Kingdom. It originated with the overseas colonies and trading posts established by England in the late 16th and early 17th centuries. At its height, it was the...

 (including the American colonies
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

), Wednesday was followed by Thursday . For 12 years from 1700 Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 used a modified Julian calendar
Swedish calendar
The Swedish calendar was a calendar in use in Sweden and its possessions from 1 March 1700 until 30 February 1712; it was one day ahead of the Julian calendar and ten days behind the Gregorian calendar...

, and adopted the Gregorian calendar in 1753, but Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 remained on the Julian calendar until 1918 ( became ), after the Russian Revolution
Russian Revolution of 1917
The Russian Revolution is the collective term for a series of revolutions in Russia in 1917, which destroyed the Tsarist autocracy and led to the creation of the Soviet Union. The Tsar was deposed and replaced by a provisional government in the first revolution of February 1917...

 (which is thus called the "October Revolution
October Revolution
The October Revolution , also known as the Great October Socialist Revolution , Red October, the October Uprising or the Bolshevik Revolution, was a political revolution and a part of the Russian Revolution of 1917...

" though it occurred in Gregorian November), while Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....

 continued to use it until 1924.

Throughout the long transition period, the Julian calendar has continued to diverge from the Gregorian. This has happened in whole-day steps, as dropped leap-years on certain centennial years in the Gregorian calendar continued to be leap years in the Julian calendar. Thus, in the year 1700 (after Feb. 29, 1700) the difference increased to 11 days; in 1800, 12; and in 1900, 13. Since 2000 was a leap year according to the Gregorian calendar, the Julian calendar remained in step with it: (Julian) fell on (Gregorian). This difference will persist through the last day of February, 2100 (Julian), which is not a Gregorian leap year, but is a Julian leap year. Monday (Julian) falls on Monday (Gregorian), a full two-week discrepancy.

Eastern Orthodox usage


Although all Eastern Orthodox
Eastern Orthodox Church
The Orthodox Church, officially called the Orthodox Catholic Church and commonly referred to as the Eastern Orthodox Church, is the second largest Christian denomination in the world, with an estimated 300 million adherents mainly in the countries of Belarus, Bulgaria, Cyprus, Georgia, Greece,...

 countries (most of them in Eastern
Eastern Europe
Eastern Europe is the eastern part of Europe. The term has widely disparate geopolitical, geographical, cultural and socioeconomic readings, which makes it highly context-dependent and even volatile, and there are "almost as many definitions of Eastern Europe as there are scholars of the region"...

 or Southeastern Europe) had adopted the Gregorian calendar (or in the case of Greece, possibly the Revised Julian calendar) by 1927, their national churches had not. The "Revised Julian calendar
Revised Julian calendar
The Revised Julian calendar, also known as the Rectified Julian calendar, or, less formally, New calendar, is a calendar, originated in 1923, which effectively discontinued the 340 years of divergence between the naming of dates sanctioned by those Eastern Orthodox churches adopting it and the...

" was proposed during a synod
Synod
A synod historically is a council of a church, usually convened to decide an issue of doctrine, administration or application. In modern usage, the word often refers to the governing body of a particular church, whether its members are meeting or not...

 in Constantinople
Constantinople
Constantinople was the capital of the Roman, Eastern Roman, Byzantine, Latin, and Ottoman Empires. Throughout most of the Middle Ages, Constantinople was Europe's largest and wealthiest city.-Names:...

 in May 1923, consisting of a solar part which was and will be identical to the Gregorian calendar until the year 2800, and a lunar part which calculated Pascha
Pascha
Pascha may refer to:*Easter, central religious feast in the Christian liturgical year*Paskha , an Easter dish served in several Slavic countries*Paska , an Easter bread served in Ukraine...

 (Easter) astronomically at Jerusalem. All Orthodox churches refused to accept the lunar part, so almost all Orthodox churches continue to celebrate Pascha according to the Julian calendar (with the exception of the Estonian Orthodox Church and the Finnish Orthodox Church
Finnish Orthodox Church
The Finnish Orthodox Church is an autonomous Orthodox archdiocese of the Patriarchate of Constantinople. The Church has a legal position as a national church in the country, along with the Evangelical Lutheran Church of Finland....

).
The solar part of the Revised Julian calendar was accepted by only some Orthodox churches. Those that did accept it, with hope for improved dialogue and negotiations with the Western denominations, were the Ecumenical Patriarchate of Constantinople
Ecumenical Patriarchate of Constantinople
The Ecumenical Patriarchate of Constantinople , part of the wider Orthodox Church, is one of the fourteen autocephalous churches within the communion of Orthodox Christianity...

, the Patriarchates of Alexandria, Antioch, the Orthodox Churches of Greece
Church of Greece
The Church of Greece , part of the wider Greek Orthodox Church, is one of the autocephalous churches which make up the communion of Orthodox Christianity...

, Cyprus, Romania
Romanian Orthodox Church
The Romanian Orthodox Church is an autocephalous Eastern Orthodox church. It is in full communion with other Eastern Orthodox churches, and is ranked seventh in order of precedence. The Primate of the church has the title of Patriarch...

, Poland
Polish Orthodox Church
The Polish Autocephalous Orthodox Church, commonly known as the Polish Orthodox Church, , is one of the autocephalous Eastern Orthodox Churches in full communion...

, Bulgaria
Bulgarian Orthodox Church
The Bulgarian Orthodox Church - Bulgarian Patriarchate is an autocephalous Eastern Orthodox Church with some 6.5 million members in the Republic of Bulgaria and between 1.5 and 2.0 million members in a number of European countries, the Americas and Australia...

 (the last in 1963), and the Orthodox Church in America
Orthodox Church in America
The Orthodox Church in America is an autocephalous Eastern Orthodox church in North America. Its primate is Metropolitan Jonah , who was elected on November 12, 2008, and was formally installed on December 28, 2008...

 (although some OCA parishes are permitted to use the Julian calendar). Thus these churches celebrate the Nativity
Nativity of Jesus
The Nativity of Jesus, or simply The Nativity, refers to the accounts of the birth of Jesus in two of the Canonical gospels and in various apocryphal texts....

 on the same day that Western Christians do, 25 December Gregorian until 2800. The Orthodox Churches of Jerusalem
Orthodox Church of Jerusalem
The Greek Orthodox Church of Jerusalem , also known as the Orthodox Patriarchate of Jerusalem, is an autocephalous Orthodox Church within the wider communion of Orthodox Christianity. Headed by the Patriarch of Jerusalem, it is regarded by Orthodox Christians as the mother church of all of...

, Russia
Russian Orthodox Church
The Russian Orthodox Church or, alternatively, the Moscow Patriarchate The ROC is often said to be the largest of the Eastern Orthodox churches in the world; including all the autocephalous churches under its umbrella, its adherents number over 150 million worldwide—about half of the 300 million...

, Serbia
Serbian Orthodox Church
The Serbian Orthodox Church is one of the autocephalous Orthodox Christian churches, ranking sixth in order of seniority after Constantinople, Alexandria, Antioch, Jerusalem, and Russia...

, Macedonia, Georgia
Georgian Orthodox and Apostolic Church
The Georgian Apostolic Autocephalous Orthodox Church is an autocephalous part of the Eastern Orthodox Church. Since the 4th century AD, Georgian Orthodoxy has been the state religion of Georgia, and it remains the country's largest religious institution....

, Ukraine
History of Christianity in Ukraine
The History of Christianity in Ukraine dates back to the earliest centuries of the apostolic church. It has remained the dominant religion in the country since its acceptance in 988 by Vladimir the Great , who instated it as the state religion of Kievan Rus', a medieval East Slavic state.Although...

, and the Greek Old Calendarists
Greek Old Calendarists
Greek Old Calendarists are groups that separated from the Orthodox Church of Greece or from the Patriarchate of Constantinople, precipitated by disagreement over the abandonment of the traditional Julian Calendar.- History :Up until the early 20th century, the Eastern Orthodox Church used the...

 and other groups continue to use the Julian calendar, thus they celebrate the Nativity on 25 December Julian (which is 7 January Gregorian until 2100). The Russian Orthodox Church
Russian Orthodox Church
The Russian Orthodox Church or, alternatively, the Moscow Patriarchate The ROC is often said to be the largest of the Eastern Orthodox churches in the world; including all the autocephalous churches under its umbrella, its adherents number over 150 million worldwide—about half of the 300 million...

 has some parishes in the West which celebrate the Nativity on 25 December Gregorian. Parishes of the Orthodox Church in America Bulgarian Diocese
Orthodox Church in America Bulgarian Diocese
The Orthodox Church in America Bulgarian Diocese is one of three ethnic dioceses of the Orthodox Church in America . Its territory includes parishes, monasteries, and missions located in six states in the United States, as well as one province in Canada – California, Illinois, Indiana, Kansas,...

, both before and after the 1976 transfer of that diocese from the Russian Orthodox Church Outside Russia
Russian Orthodox Church Outside Russia
The Russian Orthodox Church Outside Russia , also called the Russian Orthodox Church Abroad, ROCA, or ROCOR) is a semi-autonomous part of the Russian Orthodox Church....

 to the Orthodox Church in America
Orthodox Church in America
The Orthodox Church in America is an autocephalous Eastern Orthodox church in North America. Its primate is Metropolitan Jonah , who was elected on November 12, 2008, and was formally installed on December 28, 2008...

, were permitted to use the 25 December Gregorian date. Some Old Calendarist groups which stand in opposition to the state church
State church
State churches are organizational bodies within a Christian denomination which are given official status or operated by a state.State churches are not necessarily national churches in the ethnic sense of the term, but the two concepts may overlap in the case of a nation state where the state...

es of their homelands will use the Great Feast of the Theophany (6 January
January 6 (Eastern Orthodox liturgics)
Jan. 5 - Eastern Orthodox Church calendar - Jan. 7-Fixed commemorations:All fixed commemorations below are observed on January 19 by Old Calendarists-Feasts:*The Holy Theophany of Jesus, or His Baptism*Traditionally, the beginning of house blessing season...

 Julian/19 January Gregorian) as a day for religious processions
Crucession
A Crucession, or Cross Procession , is a procession that takes place in the Eastern Orthodox and Eastern Catholic liturgical traditions. The name derives from the fact that the procession is headed by a cross....

 and the Great Blessing of Waters, to publicize their cause.

The Oriental Orthodox Churches generally use the local calendar of their homelands. However, when calculating the Nativity Feast, most observe the Julian calendar. This was traditionally for the sake of unity throughout Christendom. In the West, some Oriental Orthodox Churches either use the Gregorian calendar or are permitted to observe the Nativity according to it. The Armenian Apostolic Orthodox Church celebrates the Nativity as part of the Feast of Theophany according to its traditional calendar.

Berber calendar


In Northern Africa, the Julian calendar (the Berber calendar
Berber calendar
The Berber calendar is the agricultural calendar that is traditionally used in North Africa regions. It is also known in Arabic as the fellāḥī "rustic" or ʿajamī "foreign" calendar...

) is still in use for agricultural purposes, and is called فلاحي fellāhī "peasant" or اﻋﺠﻤﻲ acjamī "not Arabic". The first of yennayer currently corresponds to 14 January and will do so until 2100.

See also

  • Computus
    Computus
    Computus is the calculation of the date of Easter in the Christian calendar. The name has been used for this procedure since the early Middle Ages, as it was one of the most important computations of the age....

  • Conversion between Julian and Gregorian calendars
    Conversion between Julian and Gregorian calendars
    The tables below list equivalent dates in the Julian and Gregorian calendars. Years are given in astronomical year numbering.-Conventions:*Within these tables, January 1 is always the first day of the year....

  • Dominical letter
    Dominical letter
    Dominical letters are letters A, B, C, D, E, F and G assigned to days in a cycle of seven with the letter A always set against 1 January as an aid for finding the day of the week of a given calendar date and in calculating Easter....

  • Easter
    Easter
    Easter is the central feast in the Christian liturgical year. According to the Canonical gospels, Jesus rose from the dead on the third day after his crucifixion. His resurrection is celebrated on Easter Day or Easter Sunday...

  • Julian day
    Julian day
    Julian day is used in the Julian date system of time measurement for scientific use by the astronomy community, presenting the interval of time in days and fractions of a day since January 1, 4713 BC Greenwich noon...

  • Julian year (astronomy)
    Julian year (astronomy)
    In astronomy, a Julian year is a unit of measurement of time defined as exactly 365.25 days of 86 400 SI seconds each, totaling 31 557 600 seconds. The Julian year is the average length of the year in the Julian calendar used in Western societies in previous centuries, and for which the unit is...

  • Mixed-style date
  • Proleptic Gregorian calendar
    Proleptic Gregorian calendar
    The proleptic Gregorian calendar is produced by extending the Gregorian calendar backward to dates preceding its official introduction in 1582.-Usage:...

  • Proleptic Julian calendar
    Proleptic Julian calendar
    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...

  • Revised Julian calendar
    Revised Julian calendar
    The Revised Julian calendar, also known as the Rectified Julian calendar, or, less formally, New calendar, is a calendar, originated in 1923, which effectively discontinued the 340 years of divergence between the naming of dates sanctioned by those Eastern Orthodox churches adopting it and the...

  • Week
    Week
    A week is a time unit equal to seven days.The English word week continues an Old English wice, ultimately from a Common Germanic , from a root "turn, move, change"...


External links