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Roman calendar

The Roman calendar changed its form several times in the time between the foundation of Rome and the fall of the Roman Empire.

Table of contents
1 Months
2 Days of the week
3 Years
4 References

Months

To begin with it was a lunar calendar containing ten months, starting at the vernal equinox, traditionally invented by Romulus, the founder of Rome about 753 BC. However it seems to have been based on the Greek lunar calendar. The months at this time were Thus the calendar year lasted 304 days and there were about 61 days of winter that did not fall within the calendar.

The first reform of the calendar was attributed to Numa Pompilius, the second of the seven traditional Kings of Rome. He is said to have reduced the 30-day months to 29 days and to have added January (29 days) and February (28 days) to the end of the calendar around 713 BC, and thus brought the length of the calendar year up to 355 days. This still left a gap of about ten days. In order to prevent the calendar year from getting out of line with the solar year, a leap month of 27 or 28 days, Mercedinus, was supposed to be added every second year at the end of February, which was shortened to 23 days.

The Romans had special names for 3 specific days in each month. The system was originally based on phases of the Luna (moon), and these days were probably declared when the lunar conditions were right. After the reforms of Numa Pompilius, they occurred on fixed days.

Months with Ides and Nones occurring on the 13th/5th day: January, February, April, June, August, September, November, December
Months with Ides and Nones occurring on the 15th/7th day: March, May, July, October --
a mnemonic:
In March, July, October, May
The IDES fall on the 15th day
The NONES the 7th.
The rest besides take 2 days less
For Nones and Ides.

Matters were further different from the modern Western calendar. The Romans did NOT count the days of the month retrospectively, looking back to the first of the month (that is: 1st, 2nd day since the start of the month, 3rd day since the start of the month). They counted forward to their named days. Also, to the distress of moderns trying to work out dates in Roman calendar documents, counted inclusively, so that September 2 is considered 4 days before September 5, rather than 3 days before.

The example of September

Kalends of September = September 1
4 days before the Nones of Sept. = September 2
3 days before the Nones of Sept. = September 3
the day before the Nones of Sept. = September 4
Nones of September = September 5
8 days before the Ides of Sept. = September 6
7 days before the Ides of Sept. = September 7
6 days before the Ides of Sept. = September 8
5 days before the Ides of Sept. = September 9
4 days before the Ides of Sept. = September 10
3 days before the Ides of Sept. = September 11
the day before the Ides of Sept. = September 12
Ides of September = September 13
18 days before the Kalends of Oct = September 14
17 days before the Kalends of Oct = September 15
16 days before the Kalends of Oct. = September 16
15 days before the Kalends of Oct. = September 17
14 days before the Kalends of Oct. = September 18
13 days before the Kalends of Oct. = September 19
12 days before the Kalends of Oct. = September 20
11 days before the Kalends of Oct. = September 21
10 days before the Kalends of Oct. = September 22
9 days before the Kalends of Oct. = September 23
8 days before the Kalends of Oct. = September 24
7 days before the Kalends of Oct. = September 25
6 days before the Kalends of Oct. = September 26
5 days before the Kalends of Oct. = September 27
4 days before the Kalends of Oct. = September 28
3 days before the Kalends of Oct. = September 29
the day before the Kalends of Oct. = September 30
Kalends of October = October 1

Notice that by counting inclusively and by having a special name for the day before a named day the Roman calendar loses the possibility of saying: 2 days before a named day.

Before the Julian calendar, the months (March, May, July and October) that had Ides on the 15th had 31 days and the other months had 29 days, except February with 28 days. Occasionally an extra month of Mercedinus was added with 22 or 23 days. This was supposed to happen on alternate years, to keep the civil year in touch with the seasons. The adding of the additional was the responsibility of the pontifex maximus, whom not always was aware of the importance of his office, and in practice happened less often, causing the need for the Julian calendar reform instituted by Julius Caesar.

An example from Shakespeare

In Shakespeare's play Julius Caesar, the dictator is warned of a plot against his life by the famous quote: Beware with the Ides of March…. History would prove the warning to be truthful because Julius Caesar was indeed killed in March 15 44 BC.

Days of the week

The days of the week were dedicated to gods, the sun or the moon. They were (note the similarities of some of the days with English, French and Spanish languages):

Years

In the early days of the Roman Republic, the years were not counted. Instead they were named after the consulss who were in power at the time (see List of Republican Roman Consuls). For instance: However, in the later Republic, years were counted from the founding of the city of Rome which was traditionally supposed to have taken place in 753 BC. Therefore, in some inscriptions the number of the years is followed by A.V.C., which stands for "AB VRBE CONDITA (meaning after the founding of the city). The letter "V" was the common sign for both "V" and "U". During the later empire, this system was used alongside the A.D. system (ANNO DIOCLETIANI) which used the year of accession of the Emperor Diocletian as the base year for counting purposes. Note that this should not be confused with the "A.D." system which the Christians introduced in mediaeval times (where "AD" stands for Anno Domini).

see also: Calendar – Julian calendar – Ancient Rome

References