Roman calendar

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

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 B.C.. However it seems to have been based on the Greek lunar calendar. The months at this time were Martius (31 days), Aprilis (30 days), Maius (31 days), Junius (30 days), Quintilis (31 days), Sextilis (30 days), September (30 days), October (31 days) , November (30 days) and December (30 days). 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 B.C., 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 names for 3 days in each month. The first named day was the Kalends, from which we get our word "calendar", which was the first day of each month. The second two named days were the Nones and the Ides. Those two named days floated - in most months they fell on the 13th and 5th of the month, but in Martius, Maius, Quintilis, and October they fell on the 7th and 15th days. The system was originally based on phases of the moon. The Kalends was the day of the New Moon. The Nones was the day of the Half Moon. The Ides was the day of the Full Moon. Before the reforms of Numa Pompilius, these days were probably declared when the lunar conditions were right. However afterwards, 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. Anyone familiar with waiting for a paycheck should understand. 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.

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, but in practice happened less often, so causing the need for reform.

see: Calendar

In the early days of the Roman Republic, the years were not counted. Instead they were named after the consuls who were in power at the time (see List of Republican Roman Consuls). 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" (= after the founding of the city). The letter "V" was the common sign for "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).

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References

Plutarch - Numa Pompilius

Ovid - Fasti