Roman calendar

Stone plate with a Roman calendar depicting fasti – official list and calendar of Roman events. The original Roman calendar was lunar and was used in the Roman empire to reform the Julius Caesar, i.e. until 46 BCE inclusive.

Na licencji Creative Commons Uznanie autorstwa - Na tych samych warunkach 3.0.

In the first years of Rome, existed Romulus year, which according to ancient sources was divided into ten months¹. The first month was March, which was named in honor of Romulus’ father – Mars. This year had only 304 days. After 30 days they received April, June, August, September, November and December. The remaining four months had 31 days. There were some discrepancies in the length of days of individual months in different parts of Italy. And so in Alba, March had 36 days, and September only 16, and October in Aricie as many as 39 days. It is now assumed that the Romulus year lasted much longer.

Another calendar reform falls on the reign of Numa Pompilius. Two new months were added then January (Januarius) and February (Februarius). The year was divided according to the course of the moon into twelve months, including leap years. Four months had 31 days, ie: March, May, July, October, February had 28 days, and the rest were 29 days each. The year in this calendar was 355 days long.
In the middle of the 5th century BCE, the decemvir commission wanted to introduce leap months and thus make the calendar more like the solar cycle. To this end, an additional month was introduced, which always began after February 23 or 24. He counted after 23 or 22 days and was called Mercedonius or Intercalaris. After the expiration of an additional month, the calculation of February continued.

From 191 BCE, priests had the right to add leap months at their own discretion under the law of Manius Acylius Glabrion. This resulted in complete arbitrariness in determining when to and when not to enter such a month. In the years 59–46 BCE, the pontiffs gave up their privilege, which was most often associated with the intervention of influential individuals. However, the changes that were introduced in previous years were irreversible. The calendar was such a mess that in 46 BCE the difference between dates and the correct date was 90 days. This in turn meant that the seasons did not coincide with the correct months. In order to organize the calendar, three additional months were introduced. In addition to the standard Mercedonius, two more months of 33 and 34 days were introduced between November and December. Macrobius called this year a year of confusion. Thus, the year 706 since the founding of Rome was 455 days.

Julian calendar

In the same year, Julius Caesar with the help of his astronomer Sozygenes from Alexandria introduced another reform of the Roman calendar. Sozyges calculated that each year consists of 365, 25 days. He determined the number of days for individual months, and made February a leap year every four years. The change, however, was not to add one day to February, as is done today, but to repeat it the same day. So every four years, every Roman lived the same day twice. It was set for February 24. The repeated day was called bissextilis and the leap year was also called bissextilis or bissextum. The beginning of the new calendar was set to January 1. January in the Julian calendar counted 29 days, February 28 days, 31 days each: March, May, July, September and November, and the remaining months were 30 days long. The previous duplicate month has been removed.

Shortly after Caesar’s assassination, priests counted a leap year not every four, but every three years. This resulted in further calendar days shifts. This was remedied by Octavian August, which in 8 BCE banned the introduction of a leap year for the next 12 years. This was related to the introduction, within 36 years of the new calendar, of 12 leap days, and not 9 as required by the reform. So it wasn’t until the 5th year CE that the reform of the calendar was successful. The earlier 50 years (from 45 BCE to 5 CE) are called “Julian error years” .

In the Roman calendar, the names of the first six months are derived from the names of the gods, with the exception of February, which took its name from the ceremony, while the remaining six are the order of the individual months from March, which is associated with the tradition of the Romulus calendar.

During the empire and dictatorship of Caesar, the names of some months were changed in honor of the rulers. And so July from Quinctilis was changed to Julius (which was related to the deification of Julius Caesar), and August to August in honor of August Octavian. these are obviously changes that have survived to this day. Their successors also changed the names of months, but they were only ephemeris and in most cases they did not survive their reign. This was done, among others, by Domitian, who, after defeating the Germans and adopting the name Germanicus, changed the name of September to Germanicus, and October to Domitianus II. After his death, the original names of these two months were restored. The furthest he did, however, went Kommodus, which changed the names of all twelve months, replacing them with the names of its nicknames. So the months in his reign were: Amazonius, Invictus (invincible), Felix (happy), Pius (pious), Lucius, Aemilius, Aurelius, Commodus, Augustus, Hercules, Romanus, Exsuperantius (highlighted).

The Roman month was divided into three eight-day units, which were called nundins. Nundins did not fall out for specific periods, because the individual eight-day units were divided all year, not individual months. So in the calendar before 46 BCE the year had 44 nundins and 3 days off, while in the Julian calendar there were already 45 days and an additional 5 days off. The eight-day cycle was seven working days, while the eighth day was a day off from c