The Roman calendar changed its form several times in the time between the foundation of Rome and the fall of the Roman Empire.
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
- 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 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 Moon (Luna), and these days were probably declared when the lunar conditions were right. After the reforms of Numa Pompilius, they occurred on fixed days.
- Kalends - first day of the month, from which the word "calendar" is derived. Interest on debt was due on Kalends.
- Nones – depending on the month, could be the 5th or the 7th day; traditionally the day of the Half Moon
- Ides – depending on the month, could be the 13th and 15th day; traditionally the day of the Full Moon
- 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 the Ides of March…. Julius Caesar was indeed killed on 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 French and Spanish languages):
- Sunday – Dies Solis (day of the sun)
- Monday – Dies Lunae (day of the moon)
- Tuesday – Dies Martis (day of Mars)
- Wednesday – Dies Mercuri (day of Mercury)
- Thursday – Dies Iovis (day of Jupiter)
- Friday – Dies Veneris (day of Venus)
- Saturday – Dies Saturni (day of Saturn)
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). For example, 205 BC was The year of the consulship of Publius Cornelius Scipio Africanus and Publius Licinius Crassus.
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 ab urbe condita (meaning after the founding of the city, and abbreviated AUC).
- Bill Hollon's site (http://www.12x30.net/linked.html)
- Early Roman Calendar - History (http://webexhibits.org/calendars/calendar-roman.html)
- Smith's Dictionary article (http://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA*/Calendarium.html)
de:Kalender (Römisches Reich)