The Roman Calendar

Epigraphy: the study of inscriptions, found on buildings, altars, bricks, plaques or tablets of various materials, tiles, mosaics, pottery--anything you can think of that people write on

From the first three centuries of the Roman Republic (500-200 B.C.), relatively few inscriptions survive. There is no way of knowing what type of role and how big writing/inscribing things played in Romans' lives at that time, but we can assume that what we do have only represents a small fraction of what they used. Ancient literature we have today refers to other works of literature and inscriptions that no longer exist, so it's easy to imagine that we have a limited portion of what ancient people had.

"An impressive variety of texts," however, has survived from the centuries that followed (200-100 B.C.)1 . We have many more inscriptions from this particular time period in the Roman Republic, including calendars!

The Structure of Roman Calendars

The period of the lunisolar calendar was what the original Roman (pre-Julian) calendar was based on. In the Lunisolar calendar, months corresponded to the phases of the moon--sometimes months were assigned by empirical observation and correction, sometimes by just giving months an appropriate and conventional number of days. When a solar year is 365.24 days, however, and a lunisolar year is made up of 12 lunar cycles that, added together, only make 354 days, a thirteenth month would be intercalated to the lunisolar calendar occasionally to harmonize the two.

One of 200 fragments of pre-Julian Roman calendars found today.

So, every month in the lunisolar calendar used by the Romans had either 28, 29, or 31 days each, and the calendar contained 12 months. Intercalary months of 22 or 23 days were required to match the 355 day lunisolar year to the 365.24 day solar year, but this task was preformed irregularly by the pontiffs.

The first day of every month in Rome was Kalends (kalendae), "the day when the size of the waning moon indicated when a new crescent moon would next appear, on a day termed Nones (nonae)" So, basically, the first day of the month was always set on a day of a new moon, and around the 5th or 7th day of every month a half moon would indicate the Nones. The Ides were supposed to correspond to the nights of the full moon (which occur on the thirteenth of every month except for March, May, October, and July--in those four months the full moon lands on the fifteenth).

Scholars assume that Rome borrowed this structure from the Etruscans, but we do know that this set-up was established early on in the Republic--it was done in order to institute a routine work week of eight days (without gaps), beginning with a market day.

Julius Caesar's Reforms

Julius Caesar

By 44 B.C., the calendar the Romans were going off of was 80 days ahead of the proper season because of the lunisolar calendar year being so different from the solar year. Using the best scientific advice, Caesar instituted a new calendar.

In order to align calendar dates with solar dates, Julius Caesar increased the number of days in several months. Intercalation only had to occur once every four years to equal 365.25 under his new calendar, and only by adding one day.

This calendar has only been changed once since its creation--in the sixteenth century Pope Gregory XIII made a minor change, adjusting the calendar to match up with the true solar year that is 365.24 days, not 365.25 days (a difference of 11 minutes which which, by the time Gregory fixed it, had caused the calendar days to be 10 days off the solar days--the error acceleration rate was about 3 days every four centuries.)

Today we STILL use this Calendar! Here is a table that shows exactly where Caesar added days:

Months	Lengths before 45 BC	Lengths as of 45 BC
Ianuarius[3]	29	31
Februarius	28 (leap years: 23 or 24)	28 (leap years: 29)
Martius	31	31
Aprilis	29	30
Maius	31	31
Iunius[3]	29	30
Quintilis[4] (Iulius)	31	31
Sextilis (Augustus)	29	31
September	29	30
October	31	31
November	29	30
December	29	31
Mercedonius/Intercalaris	0 (leap years: 27) (inserted between the shortened February and March)	(abolished)

The Role of Calendars in the Roman Republic

The monthly rhythm provided by following a calendar allowed the Romans to coordinate permanently established and annually recurring activities. Kalends, the first day of the month, was the day for paying interest! On Ides, you would repay the loan you drew out on Kalends. If your birthday fell on any day besides Ides or Kalends, you would still wait to celebrate on the nearest Ides or Kalends. The Senate often met on the Kalends and Ides, though they were not limited to these days only.

The 8-day market week was used for coordinating short-term, frequently occurring events--like judicial, economic, or political activities.

The Calendar and the Gods

"Gods could have territorial property. Some of them had temporal property, too." 1

Feriae: a particular day owned by the gods, not available for most human activities

The structure of the Roman calendar was based on the cycle of the moon and then, eventually, the sun, but Feriae were also an important component of the Roman Calendar. The term Feriae signaled a god's ownership of a particular day. For example, Jupiter owned all the Ides (the 13th or 15th of each month). No deity could permanently own more than one day--two days in a row was a no-no. One free day cushioned each day owned by a god, that is one before and one after (giving a measurable border between divine territories). Conflicts of ownership were also avoided by having a free day in between.

How could divine ownership of a day be marked? By limiting the amount of human activity that can go on that day! No popular assemblies were held during Feriae, or judicial activities involving magistrates. The Senate was free to meet, however--Feriae or not!