Julian calendar
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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.
Before the new calendar took effect, the start of
the calendar year (1
January) was realigned to the tropical year by making
46 BC
445 days long. The Julian months were formed by adding 10 days to
the months of the regular pre-Julian Roman year of 355 days. Two
extra days were added to January, July and December, and one extra
day was added to April, June, September and November. 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 towards the start of the next
month, the extra days had the effect of raising the initial value of
the count for the day after the Ides.
The old
intercalary month was abolished. The new leap day was originally
inserted following
February 24, a.d. VI Kal. Mar. by Roman reckoning, since this is
the point at which intercalary months were inserted in the
pre-Julian calendar. It was considered as extending that day to 48
hours, so it was dated as "a.d. VI bis Kal. Mar.", and is called the
bissextile day. When days in the month came to be numbered in
consecutive day order, however, the Leap Day was considered to be
the last day in February in leap years, i.e.
February 29.
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national Orthodox churches, it has generally been replaced by the
modern
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.
The notation
"Old Style" (OS) is sometimes used to indicate a date in the
Julian calendar, as opposed to
"New Style" (NS), which indicates a date in the Gregorian
Calendar. This notation is used when there might otherwise be
confusion about which date is found in a text.
Bust of Julius Caesar from the Altes Museum in
Berlin.
[edit]
From Roman to Julian
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, 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
becoming 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 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 or equinox.
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. 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, if too many intercalations were omitted, as happened after
the Second Punic War and during the Civil Wars, the calendar would
drift rapidly out of alignment with the tropical year. Moreover,
since 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 BC
to 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.
The reform was intended to correct this problem
permanently. Before it took effect, the missed intercalations during
Julius Caesar's pontificate were made up by inserting 67 days
(22+23+22) between the last pre-Julian November and December in 46
BC, in the form of two months, in addition to 23 days that had
already been added to February. Thus 90 days were added to this last
year of the Roman Republican calendar, giving it 445 days. Because
it 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.
[edit]
Leap year error
Despite the new calendar being 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. This
resulted in too many leap days.
Augustus remedied this discrepancy after 36 years of this
mistake by restoring the correct frequency. He also skipped several
leap days in order to realign the year.
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
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. It has sometimes been suggested
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.
Other solutions have been proposed from time to
time.
Kepler proposed in
1614
that the correct sequence of leap years was 43, 40, 37, 34, 31, 28,
25, 22, 19, 16, 13, 10 BC, AD 8, 12 etc. 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 that mentions a leap day in 41 BC that was said to
be contrary to (Caesar's) rule. 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. With all these solutions, except that of
Radke, the Roman calendar was not finally aligned to the Julian
calendar of later times until
26 February (a.d. V Kal. Mar.)
AD 4. On
Radke's solution, the two calendars were aligned on
26 February
1 BC.
In 1999, an Egyptian
papyrus was published that gives an
ephemeris table for
24 BC
with both Roman and Egyptian dates. From this it can be shown that
the most likely sequence was in fact 44, 41, 38, 35, 32, 29, 26, 23,
20, 17, 14, 11, 8 BC, AD 4, 8, 12 etc, very close to that proposed
by Matzat. This sequence shows that the standard Julian leap year
sequence began in
AD 4, the 12th year of the Augustan reform, and that the Roman
calendar was finally aligned to the Julian calendar in
1 BC,
as in Radke's model. The Roman year also coincided with the
proleptic Julian year between 32 and 26 BC. This suggests that one
aim of the realignment portion of the Augustan reform was to ensure
that key dates of his career, notably the fall of Alexandria on
1
August
30 BC,
were unaffected by his correction.
Roman dates before 32 BC were typically a day or
two before the day with the same Julian date, so
1
January in the Roman calendar of the first year of the Julian
reform was
31 December
46 BC
(Julian date). A curious effect of this is that Caesar's
assassination on the Ides (15th day) of March fell on
14
March
44 BC in the Julian calendar.
edit]
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. Their lengths were set to their modern values. The old
intercalary month, the
Mensis Intercalaris, 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 and
Augustus, renaming Quintilis (originally, "the Fifth month",
with March = month 1) as Iulius (July)[1]
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, fell in that month.
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Other months were renamed by other emperors, but
apparently none of the later changes survived their deaths.
Caligula renamed September ("Seventh month") as
Germanicus;
Nero
renamed Aprilis (April) as Neroneus, Maius (May) as Claudius and
Iunius (June) as Germanicus; and
Domitian renamed September as
Germanicus and October as ("Eighth month") Domitianus. At other
times, September was also renamed as
Antoninus and
Tacitus, and November ("Ninth month") was renamed as
Faustina and Romanus.
Commodus 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. He renamed all of the months agriculturally into
Old High German. They were used until the
15th century, and with some modifications until the late
18th century in Germany and in the Netherlands (January-December):
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).
[edit]
Month lengths
A 13th century scholar,
Sacrobosco, proposed an explanation for the month lengths 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 predating the Julian reform has survived,[2]
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 third and fifth century authors
Censorinus 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.
[edit]
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. Roman years were named this
way until the last consul was appointed in
541. 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 (the latter ending only four years later).
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.
[edit]
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 calendars were aligned
to start on the birthday of Augustus,
23
September. The indiction caused the
Byzantine year to begin on
1
September, which is still used in the
Eastern Orthodox Church for the beginning of the
liturgical year.
During the
Middle Ages
1 January
retained the name
New Year's Day (or an equivalent name) in all
Western European countries (affiliated with the
Roman Catholic Church), 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),
25 March
(the
Incarnation of Jesus), or even
Easter, as
in France
(see the
Liturgical year article for more details).
Most Western European countries, except for a few
Italian
states, 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
sixteenth century. The following table shows the years in which various
countries adopted
1 January
as the start of the year.
[edit]
From Julian to Gregorian
The Julian calendar was in general use in Europe and
Northern Africa from the times of the
Roman Empire until 1582, when
Pope Gregory XIII promulgated the
Gregorian Calendar, which was soon adopted by most Catholic countries.
Protestant countries followed later, and the countries of Eastern Europe
even later. In the
British Empire (including the
American colonies), Wednesday
2
September 1752
was followed by Thursday
14
September 1752.
For 12 years from
1700 Sweden
used a
modified Julian Calendar, and adopted the new-style calendar in
1753, but
Russia
remained on the Julian calendar until
1917, after the
Russian Revolution (which is thus called the 'October
Revolution', but occurred in Gregorian November), while
Greece
continued to use it until
1923.
Although all Eastern European countries had adopted the
Gregorian calendar by 1927, their national
Eastern Orthodox churches had not. A
revised Julian calendar was proposed during a synod in
Constantinople 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 Easter astronomically at
Jerusalem.
All Orthodox churches refused to accept the lunar part, so almost all
Orthodox churches continue to celebrate Easter according to the Julian
calendar (the
Finnish Orthodox Church uses the Gregorian Easter).
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, the Patriarchates of
Alexandria,
Antioch, the Orthodox Churches of
Greece,
Cyprus,
Romania,
Poland,
Bulgaria (the last in 1963), and the
Orthodox Church in America (although some OCA parishes are permitted to
use the Julian calendar). Thus these churches celebrate the Nativity on the
same day that Western Christians do,
25
December Gregorian until 2800. The Orthodox Churches of
Jerusalem,
Russia,
Macedonia,
Serbia,
Georgia,
Ukraine, and the
Greek Old Calendarists continue to use the Julian calendar for their
fixed dates, thus they celebrate the Nativity on
25
December Julian (which is
7 January
Gregorian until 2100).
In Northern Africa, the Julian calendar (the
Berber calendar) is still in use for agricultural purposes, and is
called ﻓﻼﺣﻲ fellāḥī "peasant" or ﻋﺠﻤﻲ
cajamī
"not Arabic". Since it did not follow the Gregorian reform, its beginning
slowly shifted and now the first of yennayer corresponds to January
14th.
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