Editing Roman calendar (section)

==Years==
{{main|List of Roman consuls}}
[[File:Kalender.jpg|thumb|200px|right|A fragment of an imperial [[list of Roman consuls|consular list]]<ref>[[Corpus Inscriptionum Latinarum]] I, CIL VI.</ref>]]
As mentioned above, Rome's legendary 10-month calendar notionally lasted for 304{{spaces}}days but was usually thought to make up the rest of the [[solar year]] during an unorganized winter period. The unattested but almost certain lunar year and the pre-Julian civil year were {{nowrap|354 or 355 days}} long, with the difference from the solar year more or less corrected by an irregular intercalary month. The [[Julian calendar|Julian year]] was 365{{spaces}}days long, with a [[leap day]] doubled in length every fourth year, almost equivalent to the present [[Gregorian calendar|Gregorian system]].

The [[calendar era]] before and under the [[Roman Kingdom|Roman king]]s is uncertain but dating by [[regnal year]]s was common in antiquity. Under the [[Roman Republic]], from 509 BC, years were most commonly described in terms of their reigning [[Roman consul|ordinary consuls]].<ref name=matlock/> ([[Suffect consul|Temporary]] and honorary consuls were sometimes elected or appointed but were not used in dating.)<ref name=matlock/> [[List of Roman consuls|Consular lists]] were displayed on the [[fasti|public calendars]]. After the institution of the [[Roman Empire]], regnal dates based on the emperors' terms in office became more common. Some historians of the later republic and early imperial eras dated from the legendary founding of the city of Rome (''{{lang|la|[[ab urbe condita]]}}'' or {{sc|avc}}).<ref name=matlock/> [[Varro]]'s date for this was 753 BC but other writers used different dates, varying by several decades.{{citation needed|date=April 2017}} Such dating was, however, never widespread. After the consuls waned in importance, most Roman dating was regnal<ref name=matchlock>{{harvp|Mathieson|2003|p=[https://books.google.com/books?id=krcp3GU2MssC&pg=PA15 15]}}.</ref> or followed [[Diocletian]]'s 15-year [[Indiction]] tax cycle.<ref name=matlock/> These cycles were not distinguished, however, so that "year 2 of the indiction" may refer to any of 298, 313, 328, &c.<ref name=matlock/> The [[Greek Orthodox Church|Orthodox]] subjects of the [[Byzantine Empire]] used various Christian eras, including [[Anno Martyrum|those based on Diocletian's persecutions]], [[Incarnation (Christianity)|Christ's incarnation]], and [[Anno Mundi|the supposed age of the world]].

The Romans did not have records of their early calendars but, like modern historians, assumed the year originally began in March on the basis of the names of the months following June. The consul [[Marcus Fulvius Nobilior (consul 189 BC)|M. Fulvius Nobilior]] (r. 189 BC) wrote a commentary on the calendar at his [[Temple of Hercules Musarum]] that claimed January had been named for [[Janus (god)|Janus]] because the god faced both ways,<ref name=Varro />{{where|date=April 2017}} suggesting it had been instituted as a first month.{{citation needed|date=April 2017}} It was, however, usually said to have been instituted along with February, whose nature and festivals suggest it had originally been considered the last month of the year. The consuls' term of office—and thus the order of the years under the republic—seems to have changed several times. Their inaugurations were finally moved to January 1(''{{lang|la|Kal. Ian.}}'') in 153{{nbsp}}BC to allow [[Quintus Fulvius Nobilior|Q. Fulvius Nobilior]] to attack [[Segeda]] in [[Prehistoric Spain|Spain]] during the [[Celtiberian Wars]], before which they had occurred on March 15 (''{{lang|la|[[Ides of March|Eid. Mart]].}}'').{{sfnp|Livy|loc=Book XLVII}} There is reason to believe the inauguration date had been May 1 during the {{nowrap|3rd century BC}} until 222{{nbsp}}BC{{citation needed|date=April 2017}} and [[Livy]] mentions earlier inaugurations on May 15 (''{{lang|la|Eid. Mai.}}''), July 1 (''{{lang|la|Kal. Qui.}}''), August 1 (''{{lang|la|Kal. Sex.}}''), October 1(''{{lang|la|Kal. Oct.}}''), and December 15 (''{{lang|la|Eid. Dec.}}'').{{sfnp|Livy|loc={{pages needed |date=April 2017}}}} Under the Julian calendar, the year began on January 1 but years of the [[Indiction]] cycle began on September 1.

In addition to [[Egyptian calendar|Egypt's separate calendar]], some provinces maintained their records using a local era.<ref name=matlock/> [[Africa (Roman province)|Africa]] dated its records sequentially from 39{{nbsp}}BC;<ref name=matchlock/> [[Roman Spain|Spain]] from AD{{nbsp}}38.{{citation needed|date=April 2017}} This dating system continued as the [[Spanish era]] used in [[medieval Spain]].{{citation needed|date=April 2017}}