A page from the "Calendars" exhibit...

Early Roman Calendar

The Romans borrowed parts of their earliest known calendar from the Greeks. The calendar consisted of 10 months in a year of 304 days. The Romans seem to have ignored the remaining 61 days, which fell in the middle of winter. The 10 months were named Martius, Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, and December. The last six names were taken from the words for five, six, seven, eight, nine, and ten. Romulus, the legendary first ruler of Rome, is supposed to have introduced this calendar in the 700s B.C.E.

According to tradition, the Roman ruler Numa Pompilius added January and February to the calendar. This made the Roman year 355 days long. To make the calendar correspond approximately to the solar year, Numa also ordered the addition every other year of a month called Mercedinus. Mercedinus was inserted after February 23 or 24, and the last days of February were moved to the end of Mercedinus. In years when it was inserted, Mercedinus added 22 or 23 days to the year.


Roman Fasti

Some 200 fragments of Roman calendars have been found so far, and they are collectively known as Fasti.

What did a Roman calendar look like?

The Roman calendar used a system of months, and special days in each month. Some calendars were carved in marble or stone, but many were painted on walls for decoration.

Different geographical areas often held different gods in special esteem, and this led to regional variations in calendars. This doesn’t seem so strange when one considers that even within the US, Mardi Gras often appears only on Southern calendars, and Lincoln’s birthday sometimes does not.

In 45 B.C.E., Romans modified their method of marking time to keep it in phase with seasons, but not require intercalation of an extra month. They accomplished this with the Julian Calendar. Month lengths were extended to bring the calendar’s total to 365 days, making it truly solar. This change was accompanied by addition of an extra day every fourth year (after February 23rd) because of the almost six extra hours beyond 365 days in a tropical year.

How do you read the calendar?

In the calendar of the ancient Romans, the months contained three primary markers – the Kalends, the Nones and the Ides. The Kalends were always the first day of the month. The Nones were usually the 5th but sometimes the 7th, and the Ides were the 15th but sometimes the 13th. All the days after the Ides were numbered by counting down towards the next month’s Kalends. The holidays were generally bunched together to form continuous celebrations, and the remaining days of the month were usually nondescript workdays.

The days were each identified with certain letters and names. The Kalends were always identified as shown in the diagram at right. The archaic form of the K, for Kalends, was used in front of the name of the month. The first letter was called the Nundinae ("nine day") , or the Nundinal letter, and it represented the market day. Every 9th day (counting inclusively) was a market day, but as it shifted every year, a designated letter between A and H would represent the market day for that year. The final letter identifies the type of day for purposes of religious observance or legal business.


The top diagram shows a typical non-holiday. The first letter is the nundinal letter for the market day. If the market day for this year was E then this would be a market day. The second letter signifies the type of religious or legal observance required or permitted on this day. In this case the letter C represents dies comitiales, days when committees of citizens could vote on political or criminal matters. The other letter designations :

  1. F stands for dies fasti, days on which legal action is permitted.
  2. N stands for dies nefasti, which meant that no legal action or public voting could take place on this day.
  3. EN stands for endotercisus, or intercisus, which were "in-between" F or C days in which mornings and afternoons had different designations.
  4. NP, the combination of N and P, represented some important type of religious observance of which all records have disappeared. However, they all seem to be directly associated with major holidays.
  5. FP also represented some religious holiday, but no definition survives for this abbreviation.

The center diagram is a typical festival, or feriae. On these days the day letter follows the holiday name, which is abbreviated in these calendars. These holidays are explained in the write-up for each day.

The Romans enjoyed more holidays than the number of our holidays and weekends combined. Roman taxes were also only a tithe, or 10%. One of the hallmarks of progress seems to be that the populace is always made to work longer and, on top of it all, they are taxed more.


What were the Roman weekdays?

The Romans did not have weekdays in the same sense as our Monday, Tuesday, etc., however, they did have a defined markers within each month. Originally, the month and the markers were based on the moon.

At the time of their early kings, Roman months were of a length identical to the lunar cycle. Each month was divided into sections that ended on the day of one of the first three phases of the moon: new, first quarter or full. All days were referred to in terms of one of these three moon phase names, Kalends, Nones or Ides.

At that time a pontifex (priest) was assigned to observe the sky. When he first sighted a thin lunar crescent he called out that there was a new moon and declared the next month had started. For centuries afterward, Romans referred to the first day of each month as Kalendae or Kalends from the Latin word calare (to announce solemnly, to call out). The word calendar was derived from this custom.

Day of Kalends

Of the three sections, Kalends was the longest – it had more days than the other two combined. That’s because it spanned more than two lunar phases, starting from the day after full moon and continuing thru its last quarter and waning period, then past the dark new moon until another lunar crescent was sighted. The day of Kalends itself began a new month. It was dedicated to Juno, a principal goddess of the Roman Pantheon.

Unnamed days in the early Roman month were assigned a number by counting down following the day of each named phase, day by day, ending with the next of those three phases. The first numbered day in each section had the section’s highest value. Each succeeding day was one number lower than that of the day before. (Similar to the modern count-down when coordination of a group of people is required for a complicated activity such as launching a rocket.)

Latin for "the evening before" is "Pridie," a word that was used to refer to the day before each of these named phases. So Pridie was always the day that would otherwise have been numbered two. The count-down was inclusive; the day from which they started as well as that of the moon phase to which they were counting down, day one, were both included.

Day of Nones

Nones (Latin nonus or ninth) was originally the day when the moon reached its first quarter phase. When the pontifex initially saw the lunar crescent he noted its width and, using empirical knowledge, calculated the number of days that were expected to elapse between then and the first quarter moon. He then specified that number after he announced the new crescent. If he called out the number six, the day following Kalends would be referred to as the sixth day before Nones.

In any given year, the second day of Martius might well have been designated as the sixth of the Nones of March: "ante diem VI Non. Mart." If this were the case, Nones would be the seventh day and Ides would be the 15th day of that month. The difference between these two dates, eight days, was always the length of the Ides section.

Use of the word "Nones" (nine) was intended to express the inclusive number of elapsed days between first quarter and full moons. Actually, the time between moon phases now averages about 7.4 days, but they sometimes occur eight days apart. Eight-day separations of first quarter and full moons now usually come grouped in consecutive lunations. They then give way to mostly seven-day periods.

Six of the first seven lunations of 1997, for instance, had their first quarter and full moon phases eight days apart (inclusive nine-day spans). Also, July 1 of 1998 had a first-quarter moon followed by a new moon on July 9, a nine-day period. This helps explain why the unlikely term of Nones, meaning ninth, was used to designate one fourth of the moon’s period that now averages about 29.53 days.

Day of Ides

Ides, dedicated to Jupiter, was originally the time of the full moon. Because a full moon comes halfway thru each lunation, its day was called Idus in Latin from an Etruscan word meaning "divide."

After Ides, the next new moon was expected to appear in from 15 to 17 days. Variations in the length of time before another new moon can be sighted is due to constantly changing positions of moon and Earth relative to the sun.

When did they stop using the moon for months?

Romans separated their months from the lunar cycle in the fifth century B.C.E. Month lengths then became fixed. At that time, Ides was assigned as the 15th day in all months given 31 days in length – March, May, July and October. It was designated as the 13th day in all other months. As a result, from then on the Kalends section had from 16 to 19 days, the Nones section had either four or six days and the Ides section, as before, always had eight days.

Sometime after Kalends, Nones and Ides were fixed on predetermined days of the month rather than being defined by phases of the moon, Romans used letters A thru H on the left side of each month’s calendar column to indicate days of their eight-day marketing week. The first day of each new year was represented by the letter "A."

When did the early Roman calendar begin?

The early Roman calendar originated as a local calendar in the city of Rome, supposedly drawn up by Romulus some seven or eight centuries before the Christian Era. The year began in March and consisted of 10 months, six of 30 days and four of 31 days, making a total of 304 days: it ended in December, to be followed by what seems to have been an uncounted winter gap. Numa Pompilius, according to tradition the second king of Rome (715?-673? B.C.E.), is supposed to have added two extra months, January and February, to fill the gap and to have increased the total number of days by 50, making 354. To obtain sufficient days for his new months, he is then said to have deducted one day from the 30-day months, thus having 56 days to divide between January and February. But since the Romans had, or had developed, a superstitious dread of even numbers, January was given an extra day; February was still left with an even number of days, but as that month was given over to the infernal gods, this was considered appropriate. The system allowed the year of 12 months to have 355 days, an uneven number.

When did the Roman republican calendar begin?

The so-called Roman republican calendar was supposedly introduced by the Etruscan Tarquinius Priscus (616-579 B.C.E.), according to tradition the fifth king of Rome.

The Roman republican calendar was a dating system that evolved in Rome prior to the Christian era. According to legend, Romulus, the founder of Rome, instituted the calendar in about 738 B.C.E. This dating system, however, was probably a product of evolution from the Greek lunar calendar, which in turn was derived from the Babylonian. The original Roman calendar appears to have consisted only of 10 months and of a year of 304 days. The remaining 61¼ days were apparently ignored, resulting in a gap during the winter season. The months bore the names Martius, Aprilis, Maius, Juniius, Quintilis, Sextilis, September, October, November, and December–the last six names correspond to the Latin words for the numbers 5 through 10. The Roman ruler Numa Pompilius is credited with adding January at the beginning and February at the end of the calendar to create the 12-month year. In 452 B.C.E., February was moved between January and March.

By the 1st century B.C.E., the Roman calendar had become hopelessly confused. The year, based on cycles and phases of the moon, totaled 355 days, about 10¼ days shorter than the solar year. The occasional intercalation of an extra month of 27 or 28 days, called Mercedonius, kept the calendar in step with the seasons. The confusion was compounded by political maneuvers. The Pontifex Maximus and the College of Pontiffs had the authority to alter the calendar, and they sometimes did so to reduce or extend the term of a particular magistrate or other public official. Finally, in 46 B.C.E., Julius Caesar initiated a thorough reform that resulted in the establishment of a new dating system, the Julian calendar.

He wanted the year to begin in January since it contained the festival of the god of gates (later the god of all beginnings), but expulsion of the Etruscan dynasty in 510 B.C.E. led to this particular reform’s being dropped. The Roman republican calendar still contained only 355 days, with February having 28 days; March, May, July, and October 31 days each; January, April, June, August, September, November, and December 29 days. It was basically a lunar calendar and short by 10¼ days of a 365¼ -day tropical year. In order to prevent it from becoming too far out of step with the seasons, an intercalary month, Intercalans, or Mercedonius (from merces, meaning wages, since workers were paid at this time of year), was inserted between February 23 and 24. It consisted of 27 or 28 days, added once every two years, and in historical times at least, the remaining five days of February were omitted. The intercalation was therefore equivalent to an additional 22 or 23 days, so that in a four-year period the total days in the calendar amounted to (4 x 355) + 22 + 23, or 1,465: this gave an average of 366.25 days per year.

Intercalation was the duty of the Pontifices, a board that assisted the chief magistrate in his sacrificial functions. The reasons for their decisions were kept secret, but, because of some negligence and a measure of ignorance and corruption, the intercalations were irregular, and seasonal chaos resulted. In spite of this and the fact that it was over a day too long compared with the tropical year, much of the modified Roman republican calendar was carried over into the Gregorian calendar now in general use.

What were the Roman months?

Much of the knowledge we now have about early Roman calendars came from Ovid, a Roman born in 43 B.C.E., and from Plutarch, a Greek biographer who wrote between C.E. 105 and 115. Both of them had access to historical documents that are no longer extant. Ovid claimed that his information was "dug up in archaic calendars," so it was already ancient over two thousand years ago.

We can assume that the Roman calendar was brought from their birthplace by Rome’s original citizens. Initially, it contained only ten months. It has been suggested that those month lengths reflected growth cycles of crops and cattle. When compared with the solar year, it had an uncounted winter period of approximately sixty days.

Plutarch said that months at the time of Rome’s founding were of varying lengths, some as short as twenty days and others with thirty-five or more in what early Romans believed was a year of three hundred and sixty days. Romulus, the legendary first king, was said to have made extensive changes to those month lengths, assigning twenty-nine days to some and thirty-one to others.

Read excerpt of Plutarch’s essay.

March (the first month)

Both Ovid and Plutarch said that Martius, originally the first month, was named after Mars, the Roman god of war. Six of the other original ten were simply numbered as Quintilis thru Decembris (fifth thru tenth) but there were already disagreements when Ovid wrote, two thousand years ago, as to the sources of names for what were originally the second thru fourth, Aprilis, Maius and Junius. These disagreements continue to the present time.


When writing about April, Ovid said "I have come to the fourth month, full of honor for you; Venus, you know both the poet and the month are yours." It was later said that "April was sacred to Venus, and her festival – the Festum Veneris and Fortuna Virilis – occurred on the first day of this month." Apparently Aprilis stems from aphrilis, corrupted from Aphrodite, a Greek name for Venus. Jakob Grimm, a later authority, opposed this stating it may have originated from the name of a god or hero named Aper or Aprus."


Maius was said by some to be named after the goddess Maia, a daughter of Atlas, and Junius "is indirectly named after the goddess Juno, the Roman equivalent of Frigga." But Ovid suggested that names of months we now call May and June possibly refer not to sky-gods but rather to elders and young men.

January (at the end of the year)

There was also disagreement in Ovid’s day as to the sequence and time at which Januarius and Februarius were added to the original ten months. Januarius became part of the calendar within half a century after Rome was founded because Plutarch said that Numa, the king who followed Romulus, made it the first month of the year and made February the last. One historian assigns that action an exact date by stating that "January and February were added to an original Roman calendar of only ten months in 713 B.C.E."

January was named after Janus, a sky-god who was ancient even at the time of Rome’s founding. Ovid quoted Janus as saying "The ancients called me chaos, for a being from of old am I." After describing the world’s creation, he again quoted Janus: "It was then that I, till that time a mere ball, a shapeless lump, assumed the face and members of a god." A Lydian named Joannes identified Janus as a planet when he wrote: "Our own Philadelphia still preserves a trace of the ancient belief. On the first day of the month there goes in procession no less a personage than Janus himself, dressed up in a two-faced mask, and people call him Saturnus, identifying him with Kronos."

Early Romans believed that the beginning of each day, month and year were sacred to Janus. They thought he opened the gates of heaven at dawn to let out the morning, and that he closed them at dusk. This eventually led to his worship as the god of all doors, gates, and entrances.

Some say Februarius got its name from a goatskin thong called a februa ("means of purification.") On the 15th day of this month Romans observed the festival of Lupercalia. During the festival, a februa was wielded by priests who used it to beat women in the belief that it would make a barren woman fertile. However, there’s a Latin verb februare, meaning to "expiate" or "purify." It seems more reasonable to assume the purification people had in mind when naming the month was that of the calendar year’s length, not that of women upon whom the thong was applied.

Februrary (at the end of the year)

Apparently Februarius, when adopted, had but 23 days – traditionally the 23rd day of that month was the end of the calendar year. That indicates Februarius was observed in pre-Romulan times when months had as few as twenty days. Also, adding five days at year-end (to extend February’s length to 28) is similar to the change made by many other peoples who, around the time of Rome’s founding, added five days to their own calendar, but considered them to be unlucky and not part of the normal year.

Why is our leap day in Februrary, not the end of the year?

Romans always reconciled differences between calendar and solar year lengths during the "Month of Purification." Whenever and however Roman calendars were modified to correspond to year length, it was always done after the 23rd day of February, traditionally the last day of the year. Even in our time, leap year is observed with a 29-day February. To purists, "leap day" is February 24, not the 29th.

Plutarch wrote: "Numa...added an intercalary month, to follow February, consisting of twenty-two days, and called by the Romans the month Mercedinus. This amendment, however, itself, in course of time, came to need other amendments." (When observed, that leap month always immediately followed February 23.)

According to historian Livy, Numa divided the year into twelve months, corresponding to the moon’s revolutions. But as the moon does not complete thirty days in each month, and so there are fewer days in the lunar year than in that measured by the course of the sun, he interpolated intercalary months and so arranged them that every twentieth year the days should coincide with the same position of the sun as when they started, the whole twenty years being thus complete. He also established a distinction between the days on which legal business could be transacted and those on which it could not, because it would sometimes be advisable that there should be no business transacted with the people.

Others claim that it wasn’t until 452 B.C.E. that a month named Intercalaris was added to the Roman calendar in order to add those days required to bring calendar length back into phase with the solar year. This month also began after the 23rd day of Februarius. It was observed every second year and was said to have had a length of either 22 or 23 days, with the remaining five days of Februarius added after them.

Beware the Ides of March!

CAESAR.Ha! Who calls?
CASCA.Bid every noise be still.–Peace yet again!
[Music ceases.]
CAESAR.Who is it in the press that calls on me? I hear a tongue, shriller than all the music, Cry "Caesar"! Speak, Caesar is turn’d to hear.
SOOTHSAYER.Beware the Ides of March.
CAESAR.What man is that?
BRUTUS.A soothsayer bids you beware the Ides of March.
CAESAR.Set him before me; let me see his face.
CASSIUS.Fellow, come from the throng; look upon Caesar.
CAESAR.What say'st thou to me now? Speak once again.
SOOTHSAYER.Beware the Ides of March.
CAESAR.He is a dreamer; let us leave him. Pass.
[Sennet. Exeunt all but BRUTUS and CASSIUS.]

If you’ve heard the warning, "Beware the Ides of March," then it’s probably due to the works of William Shakespeare. The Roman ruler, Julius Caesar, was assassinated on the Ides of March - March 15, 44 B.C.E. In Shakespeare’s play Julius Caesar, (I, ii, 33), a soothsayer tells Caesar who is already on his way to the Senate (and his death), "Beware the Ides of March."

Caesar asks him to come closer and repeat what he has just said. He studies the man’s face, listens to the warning again, but decIdes, "He is a dreamer, let us leave him. Pass." There is irony here, because the audience knows (from history) that Caesar will be killed on the Ides, and that he is exercising poor judgement in dismissing this prophecy. Later, when he meets the Soothsayer again on the way to the Senate, he confidently says to him, "The Ides of March have come." But the Soothsayer reminds him, "Ay, Caesar, but not gone." There will be other warnings to Caesar from different people, which he will ignore, and go off to meet his death. The phrase "Beware the Ides of March" is one of the most remembered lines of Shakespeare’s plays.

The unidentified soothsayer from Shakespeare’s play may have been a Roman astrologer by the name of Spurinna. According to to historical writer C.J.S. Thompson (and confirmed in Plutarch’s account of the story written in 75 C.E.) it was reportedly sometime prior to the fateful day of March 15 that Spurinna had first given Caesar the famous warning to "beware of the Ides of March." The astrologer, Spurinna, had previously warned Caesar that on the Ides of March, he would be in great danger. If, however, Julius Caesar took care on that one day - then all would be well.

According to Plutarch, Caesar had previously made the wise decision to stay within the safety of his bedroom chambers on the 15th of March. However, Caesar’s "friend" Decimus (Albinus) Brutus (not Marcus Brutus) managed to convince him that the astrologer’s warnings were nothing more than superstitious foolishness. So Julius Caesar decided to attend the Senate on the 15th of March. On his way to the Senate, Caesar "accidentally" met up with the astrologer, Spurinna. Caesar then told the astrologer "The Ides of March are come." Spurinna answered, "Yes, they are come, but they are not past." Later that day - on March 15, 44 B.C.E - Caesar’s enemies assassinated him in the Pompey theater, at the foot of Pompey’s statue, where the Roman Senate was meeting that day in the temple of Venus.