Julian calendar
[7] Caesar's reform was intended to solve this problem permanently, by creating a calendar that remained aligned to the sun without any human intervention.
He landed in the Nile delta in October 48 BC and soon became embroiled in the Ptolemaic dynastic war, especially after Cleopatra managed to be "introduced" to him in Alexandria.
[15] Caesar returned to Rome in 46 BC and, according to Plutarch, called in the best philosophers and mathematicians of his time to solve the problem of the calendar.
When Caesar decreed the reform, probably shortly after his return from the African campaign in late Quintilis (July), he added 67 more days by inserting two extraordinary intercalary months between November and December.
In the early Julio-Claudian period a large number of festivals were decreed to celebrate events of dynastic importance, which caused the character of the associated dates to be changed to NP.
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.
All later writers, including Macrobius about 430, Bede in 725, and other medieval computists (calculators of Easter) followed this rule, as does the liturgical calendar of the Roman Catholic Church.
It was incorporated into Justinian's Digest,[29] and in the English Statute De Anno et Die Bissextili of 1236,[30] which was not formally repealed until 1879.
However, he also reports that in AD 44, and on some previous occasions, the market day was changed to avoid a conflict with a religious festival.
[32] Although Greek astronomers had known, at least since Hipparchus,[33] a century before the Julian reform, that the tropical year was slightly shorter than 365.25 days, the calendar did not compensate for this difference.
As a result, the calendar year gains about three days every four centuries compared to observed equinox times and the seasons.
This error continued for thirty-six years by which time twelve intercalary days had been inserted instead of the number actually due, namely nine.
Pierre Brind'Amour[51] argued that "only one day was intercalated between 1/1/45 and 1/1/40 (disregarding a momentary 'fiddling' in December of 41)[52] to avoid the nundinum falling on Kal.
[citation needed] It was decreed by the proconsul that the first day of the year in the new calendar shall be Augustus' birthday, a.d. IX Kal.
But since the corresponding Roman date in the inscription is 24 January, this must be according to the incorrect calendar which in 8 BC Augustus had ordered to be corrected by the omission of leap days.
[61] 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.
However, in eastern Europe older seasonal month names continued to be used into the 19th century, and in some cases are still in use, in many languages, including: Belarusian, Bulgarian, Croatian, Czech, Finnish,[72] Georgian, Lithuanian, Macedonian, Polish, Romanian, Slovene, Ukrainian.
Beginning in 153 BC, consuls began to take office on 1 January, thus synchronizing the commencement of the consular and calendar years.
In 537, Justinian required that henceforth the date must include the name of the emperor and his regnal year, in addition to the indiction and the consul, while also allowing the use of local eras.
The system of consular dating, long obsolete, was formally abolished in the law code of Leo VI, issued in 888.
Only rarely did the Romans number the year from the founding of the city (of Rome), ab urbe condita (AUC).
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 3rd 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.
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.
In recent years, some users of the Berber calendar have adopted an era starting in 950 BC, the approximate date that the Libyan pharaoh Sheshonq I came to power in Egypt.
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.
In contemporary as well as modern texts that describe events during the period of change, it is customary to clarify to which calendar a given date refers by using an O.S.
While Hipparchus and presumably Sosigenes were aware of the discrepancy, although not of its correct value,[90] it was evidently felt to be of little importance at the time of the Julian reform (46 BC).
[93] Most branches of the Eastern Orthodox Church use the Julian calendar for calculating the date of Easter, upon which the timing of all the other moveable feasts depends.
[97] Foula in Shetland, Scotland, a small settlement on a remote island of the archipelago, still celebrates festivities according to the Julian calendar.
