page_title: Ianuarius
section_title: Dates
hierarchical_section_title: Ianuarius / Dates
context_page_description: Ianuarius, fully Mensis Ianuarius, was the first month of the ancient Roman calendar, from which the Julian and Gregorian month of January derived. It was followed by Februarius. In the calendars of the Roman Republic, Ianuarius had 29 days. Two days were added when the calendar was reformed under Julius Caesar in 45 BCE.
  In the oldest Roman calendar, which the Romans believed to have been instituted by their legendary founder Romulus, the first month was Martius, and the calendar year had only ten months. Ianuarius and Februarius were supposed to have been added by Numa Pompilius, the second king of Rome, originally at the end of the year. It is unclear when the Romans reset the course of the year so that January and February came first. Ianuarius is conventionally thought to have taken its name from Janus, the dual-faced god of beginnings, openings, passages, gates and doorways, but according to ancient Roman farmers' almanacs Juno was the tutelary deity of the month.
context_section_description: The Romans did not number days of a month sequentially from the 1st through the last day. Instead, they counted back from the three fixed points of the month: the Nones (5th or 7th, depending on the length of the month), the Ides (13th or 15th), and the Kalends (1st) of the following month. The Nones of January fell on the 5th, and the Ides on the 13th. The last day of January was the pridie Kalendas Februarias, "day before the Kalends of February". Roman counting was inclusive; January 9 was ante diem V Idūs Ianuarias, "the 5th day before the Ides (13th) of January," usually abbreviated a.d. V Id. Ian. (or with the a.d. omitted altogether); January 23 was X Kal. Feb., "the 10th day before the Kalends of February."
  On the calendar of the Roman Republic and early Principate, each day was marked with a letter to denote its religiously lawful status. In January, these were:
  F for dies fasti, days when it was legal to initiate action in the courts of civil law;
  C, for dies comitalis, a day on which the Roman people could hold assemblies (comitia), elections, and certain kinds of judicial proceedings;
  N for dies nefasti, when these political activities and the administration of justice were prohibited;
  NP, the meaning of which remains elusive, but which marked feriae, public holidays;
  EN for endotercissus, an archaic form of intercissus, "cut in half," meaning days that were nefasti in the morning, when sacrifices were being prepared, and in the evening, while sacrifices were being offered, but were fasti in the middle of the day.
  Days were also marked with nundinal letters in cycles of A B C D E F G H, to mark the "market week" (these are omitted in the table below).
  January had two feriae conceptivae, moveable feasts that might occur on varying days to be announced by the Roman pontiffs. These were Compitalia ("Crossroads Festival") and Sementivae ("Festival of Sowing"), which the table below shows on the dates when they seem to have been observed most often.
  A dies natalis was an anniversary such as a temple founding or rededication, sometimes thought of as the "birthday" of a deity. During the Imperial period, some of the traditional festivals localized at Rome became less important, and the birthdays and anniversaries of the emperor and his family gained prominence as Roman holidays. On the calendar of military religious observances known as the Feriale Duranum, sacrifices pertaining to Imperial cult outnumber the older festivals. After the mid-1st century AD, a number of dates are added to calendars for spectacles and games (circenses) held in honor of various deities in the venue called a "circus". By the late 2nd century AD, extant calendars no longer show days marked with letters (F, N, C and so on) to show their religious status, probably in part as a result of calendar reforms undertaken by Marcus Aurelius. Festivals marked in large letters on extant fasti, represented by festival names in all capital letters on the table, are thought to have been the most ancient holidays, becoming part of the calendar before 509 BC.
  Ianuarius was expanded from 29 to 31 days on the Julian calendar. On the table below, dates after the Ides are those of the Julian calendar, with the pre-Julian date for festivals noted parenthetically. Unless otherwise noted, the dating and observances are taken from H.H. Scullard,
caption: Wall painting from Pompeii depicting men wearing the toga praetexta and thought to be celebrating the Compitalia
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