Roman calendar

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A reproduction of the fragmentary Fasti Antiates Maiores
(c. 60 BC), with the seventh and eighth months still named Quintilis ("QVI") and Sextilis ("SEX") and an intercalary month ("INTER") in the far righthand column Roman-calendar.png
A reproduction of the fragmentary Fasti Antiates Maiores(c.60BC), with the seventh and eighth months still named Quintilis ("QVI") and Sextilis ("SEX") and an intercalary month ("INTER") in the far righthand column
Another reproduction of the Fasti Antiates Maiores Museo del Teatro Romano de Caesaraugusta.43.jpg
Another reproduction of the Fasti Antiates Maiores

The Roman calendar was the calendar used by the Roman kingdom and republic. The term often includes the Julian calendar established by the reforms of the dictator Julius Caesar and emperor Augustus in the late 1st century BC and sometimes includes any system dated by inclusive counting towards months' kalends, nones, and ides in the Roman manner. The term usually excludes the Alexandrian calendar of Roman Egypt, which continued the unique months of that land's former calendar; the Byzantine calendar of the later Roman Empire, which usually dated the Roman months in the simple count of the ancient Greek calendars; and the Gregorian calendar, which refined the Julian system to bring it into still closer alignment with the solar year and is the basis of the current international standard.

Calendar system of organizing days for social, religious, commercial, or administrative purposes.

A calendar is a system of organizing days for social, religious, commercial or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months and years. A date is the designation of a single, specific day within such a system. A calendar is also a physical record of such a system. A calendar can also mean a list of planned events, such as a court calendar or a partly or fully chronological list of documents, such as a calendar of wills.

Roman Republic Period of ancient Roman civilization (509–27 BC)

The Roman Republic was the era of classical Roman civilization beginning with the overthrow of the Roman Kingdom, traditionally dated to 509 BC, and ending in 27 BC with the establishment of the Roman Empire. It was during this period that Rome's control expanded from the city's immediate surroundings to hegemony over the entire Mediterranean world.

The Julian calendar, proposed by Julius Caesar in 708 AUC (46 BC/BCE), was a reform of the Roman calendar. It took effect on 1 January 709 AUC (45 BC/BCE), by edict. It was designed with the aid of Greek mathematicians and Greek astronomers such as Sosigenes of Alexandria.


Roman dates were counted inclusively forward to the next of three principal days: the first of the month (the kalends), a day less than the middle of the month (the ides), and eight days—nine, counting inclusively—before this (the nones). The original calendar consisted of 10 months beginning in spring with March; winter was left as an unassigned span of days. These months ran for 38 nundinal cycles, each forming an eight-day week (nine days counted inclusively, hence the name) ended by religious rituals and a public market. The winter period was later divided into two months, January and February. The legendary early kings Romulus and Numa Pompilius were traditionally credited with establishing this early fixed calendar, which bears traces of its origin as an observational lunar one. In particular, the kalends, nones, and ides seem to have derived from the first sighting of the crescent moon, the first-quarter moon, and the full moon respectively. The system ran well short of the solar year, and it needed constant intercalation to keep religious festivals and other activities in their proper seasons. For superstitious reasons, such intercalation occurred within the month of February even after it was no longer considered the last month.

March is the third month of the year and named after Mars in both the Julian and Gregorian calendars. It is the second of seven months to have a length of 31 days. In the Northern Hemisphere, the meteorological beginning of spring occurs on the first day of March. The March equinox on the 20 or 21 marks the astronomical beginning of spring in the Northern Hemisphere and the beginning of autumn in the Southern Hemisphere, where September is the seasonal equivalent of the Northern Hemisphere's March. Birthday Number the letter "M".

Nundinae rest days in the ancient Roman calendar

The nundinae, sometimes anglicized to nundines, were the market days of the ancient Roman calendar, forming a kind of weekend including, for a certain period, rest from work for the ruling class (Patricians).

Week unit of time

A week is a time unit equal to seven days. It is the standard time period used for cycles of rest days in most parts of the world, mostly alongside—although not strictly part of—the Gregorian calendar.

After the establishment of the Roman Republic, years began to be dated by consulships and control over intercalation was granted to the pontifices, who eventually abused their power by lengthening years controlled by their political allies and shortening the years in their rivals' terms of office. Having won his war with Pompey, Caesar used his position as Rome's chief pontiff to enact a calendar reform in 46 BC, coincidentally making the year of his third consulship last for 446 days. In order to avoid interfering with Rome's religious ceremonies, the reform added all its days towards the ends of months and did not adjust any nones or ides, even in months which came to have 31 days. The Julian calendar was supposed to have a single leap day on 24 February (a doubled VI Kal. Mart. ) every fourth year but following Caesar's assassination the priests figured this using inclusive counting and mistakenly added the bissextile day every three years. In order to bring the calendar back to its proper place, Augustus was obliged to suspend intercalation for one or two decades. The revised calendar remained slightly longer than the solar year; by the 16th century the date of Easter had shifted so far away from the vernal equinox that Pope Gregory XIII ordered the calendar’s adjustment, resulting in the Gregorian calendar.

Overthrow of the Roman monarchy

The overthrow of the Roman monarchy, a political revolution in ancient Rome, took place around 509 BC and resulted in the expulsion of the last king of Rome, Lucius Tarquinius Superbus, and the establishment of the Roman Republic.

A consul held the highest elected political office of the Roman Republic, and ancient Romans considered the consulship the highest level of the cursus honorum.

Pontifex maximus The chief high priest of the College of Pontiffs in ancient Rome

The Pontifex Maximus was the chief high priest of the College of Pontiffs in ancient Rome. This was the most important position in the ancient Roman religion, open only to patricians until 254 BC, when a plebeian first occupied this post. A distinctly religious office under the early Roman Republic, it gradually became politicized until, beginning with Augustus, it was subsumed into the Imperial office. Its last use with reference to the emperors is in inscriptions of Gratian who, however, then decided to omit the words "pontifex maximus" from his title. Although in fact the most powerful office of Roman priesthood, the pontifex maximus was officially ranked fifth in the ranking of the highest Roman priests, behind the rex sacrorum and the flamines maiores.


The remains of the Fasti Praenestini Fasti Praenestini Massimo n1.jpg
The remains of the Fasti Praenestini

Prehistoric lunar calendar

The original Roman calendar is believed to have been an observational lunar calendar [1] whose months began from the first signs of a new crescent moon. Because a lunar cycle is about 29 12 days long, such months would have varied between 29 and 30 days. Twelve such months would have fallen 10 or 11 days short of the solar year; without adjustment, such a year would have quickly rotated out of alignment with the seasons in the manner of the Islamic calendar. Given the seasonal aspects of the later calendar and its associated religious festivals, this was presumably avoided through some form of intercalation or through the suspension of the calendar during winter.

Lunar calendar type of calendar

A lunar calendar is a calendar based upon the monthly cycles of the Moon's phases, in contrast to solar calendars, whose annual cycles are based only directly upon the solar year. The most commonly used calendar, the Gregorian calendar, is a solar calendar system that originally evolved out of a lunar calendar system. A purely lunar calendar is also distinguished from a lunisolar calendar, whose lunar months are brought into alignment with the solar year through some process of intercalation. The details of when months begin varies from calendar to calendar, with some using new, full, or crescent moons and others employing detailed calculations.

Lunar phase appearance of the illuminated (sunlit) portion of the Moon as seen by an observer

The lunar phase or phase of the Moon is the shape of the directly sunlit portion of the Moon as viewed from Earth. The lunar phases gradually and cyclically change over the period of a synodic month, as the orbital positions of the Moon around Earth and of Earth around the Sun shift.

Islamic calendar lunar calendar used by Muslims to determine religious observances

The Islamic, Muslim, or Hijri calendar is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the annual period of fasting and the proper time for the pilgrimage to Mecca. The civil calendar of almost all countries where the religion is predominantly Muslim is the Gregorian calendar. Notable exceptions to this rule are Iran and Afghanistan, which use the Solar Hijri calendar. Rents, wages and similar regular commitments are generally paid by the civil calendar.

Rome's 8-day week, the nundinal cycle, was shared with the Etruscans, who used it as the schedule of royal audiences. It was presumably a part of the early calendar and was credited in Roman legend variously to Romulus and Servius Tullius.

Romulus one of the twin brothers of Romes foundation myth

Romulus was the legendary founder and first king of Rome. Various traditions attribute the establishment of many of Rome's oldest legal, political, religious, and social institutions to Romulus and his contemporaries. Although many of these traditions incorporate elements of folklore, and it is not clear to what extent a historical figure underlies the mythical Romulus, the events and institutions ascribed to him were central to the myths surrounding Rome's origins and cultural traditions.

Servius Tullius legendary king of Rome

Servius Tullius was the legendary sixth king of Rome, and the second of its Etruscan dynasty. He reigned 575–535 BC. Roman and Greek sources describe his servile origins and later marriage to a daughter of Lucius Tarquinius Priscus, Rome's first Etruscan king, who was assassinated in 579 BC. Servius is said to have been the first Roman king to accede without election by the Senate, having gained the throne by popular support; and the first to be elected by the Senate alone, without reference to the people.

Legendary 10 month calendar

The Romans themselves described their first organized year as one with ten fixed months, each of 30 or 31 days. [2] [3] Such a decimal division fitted general Roman practice. [4] The four 31 day months were called "full" ( pleni ) and the others "hollow" ( cavi ). [5] [6] Its 304 days made up exactly 38  nundinal cycles. The system is usually said to have left the remaining 50 odd days of the year as an unorganized "winter", although Licinius Macer's lost history apparently stated the earliest Roman calendar employed intercalation instead [7] [8] and Macrobius claims the 10 month calendar was allowed to shift until the summer and winter months were completely misplaced, at which time additional days belonging to no month were simply inserted into the calendar until it seemed things were restored to their proper place. [9] [10]

Macrobius, fully Macrobius Ambrosius Theodosius, also known as Theodosius, was a Roman provincial who lived during the early fifth century, at the transition of the Roman to the Byzantine Empire, and when Latin was as widespread as Greek among the elite. He is primarily known for his writings, which include the widely copied and read Commentarii in Somnium Scipionis, which was one of the most important sources for Platonism in the Latin West during the Middle Ages, the Saturnalia, a compendium of ancient Roman religious and antiquarian lore, and De differentiis et societatibus graeci latinique verbi, which is now lost.

Later Roman writers credited this calendar to Romulus, [11] [12] their legendary first king and culture hero, although this was common with other practices and traditions whose origin had been lost to them. Some scholars doubt the existence of this calendar at all, as it is only attested in late Republican and Imperial sources and apparently supported only by the misplaced names of the months from September to December. [13] Rüpke also finds the coincidence of the length of the supposed "Romulan" year with the length of the first ten months of the Julian calendar to be suspicious.[ clarification needed ] [13]

Calendar of Romulus
in days
[2] [3]
March Mensis Martius Month of Mars 31
April Mensis Aprilis Month of Apru (Aphrodite) [14] 30
May Mensis Maius Month of Maia [15] 31
June Mensis Iunius Month of Juno 30
Quintilis Mensis Quintilis
Mensis Quinctilis [16]
Fifth Month31
Sextilis Mensis Sextilis Sixth Month30
September Mensis September Seventh Month30
October Mensis October Eighth Month31
November Mensis November Ninth Month30
December Mensis December Tenth Month30

Other traditions existed alongside this one, however. Plutarch's Parallel Lives recounts that Romulus's calendar had been solar but adhered to the general principle that the year should last for 360 days. Months were employed secondarily and haphazardly, with some counted as 20 days and others as 35 or more. [17] [18]

Republican calendar

The attested calendar of the Roman Republic was quite different. It followed Greek calendars in assuming a lunar cycle of 29 12 days and a solar year of 12 12 synodic months (368 34 days), which align every fourth year after the addition of two intercalary months. [6] The additional two months of the year were January and February; the intercalary month was sometimes known as Mercedonius. [6]

The Romans did not follow the usual Greek practice in alternating 29- and 30-day months and a 29- or 30-day intercalary month every other year. Instead, their 3rd, 5th, 7th, and 10th months [lower-alpha 1] had 31 days each; all the other months had 29 days except February, which had 28 days for three years and then 29 every fourth year. The total of these months over a 4-year span differed from the Greeks by 5 days, meaning the Roman intercalary month always had 27 days. Similarly, within each month, the weeks did not vary in the Greek fashion between 7 and 8 days; instead, the full months had two additional days in their first week and the other three weeks of every month ran for 8 days ("nine" by Roman reckoning). [19] Still more unusually, the intercalary month was not placed at the end of the year but within the month of February after the Terminalia on the 23rd ( a.d. VII Kal. Mart. ); the remaining days of February followed its completion. This seems to have arisen from Roman superstitions concerning the numbering and order of the months.[ citation needed ] The arrangement of the Roman calendar similarly seems to have arisen from Pythagorean superstitions concerning the luckiness of odd numbers. [19]

These Pythagorean-based changes to the Roman calendar were generally credited by the Romans to Numa Pompilius, Romulus's successor and the second of Rome's seven kings,[ citation needed ] as were the two new months of the calendar. [20] [21] [lower-alpha 2] Most sources thought he had established intercalation with the rest of his calendar.[ citation needed ] Although Livy's Numa instituted a lunar calendar, the author claimed the king had instituted a 19-year system of intercalation equivalent to the Metonic cycle [22] centuries before its development by Babylonian and Greek astronomers. [lower-alpha 3] Plutarch's account claims he ended the former chaos of the calendar by employing 12 months totaling 354 days—the length of the lunar and Greek years—and biennial intercalary months of 22 days. [17] [18]

According to Livy's Periochae, the beginning of the consular year changed from March to January 1 in 154 BC in order to respond to a rebellion in Hispania. [24] Plutarch believed Numa was responsible for placing January and February first in the calendar; [17] [18] Ovid states January began as the first month and February the last, with its present order owing to the Decemvirs. [25] [26] W. Warde Fowler believed the Roman priests continued to treat January and February as the last months of the calendar throughout the Republican period. [27]

Roman Republican calendar
in days
[28] [29] [17] [18]
January Mensis Ianuarius Month of Janus 29
February Mensis Februarius Month of the Februa 28
Intercalary Month
Mensis Intercalaris
Month of Wages23
March Mensis Martius Month of Mars 31
April Mensis Aprilis Uncertain29
May Mensis Maius Uncertain31
June Mensis Iunius Month of Juno 29
Quintilis Mensis Quintilis
Mensis Quinctilis [16]
Fifth Month31
Sextilis Mensis Sextilis Sixth Month29
September Mensis September Seventh Month29
October Mensis October Eighth Month31
November Mensis November Ninth Month29
December Mensis December Tenth Month29

The consuls' terms of office were not always a modern calendar year, but ordinary consuls were elected or appointed annually. The traditional list of Roman consuls used by the Romans to date their years began in 509 BC. [30]

Flavian reform

Gnaeus Flavius, a secretary (scriba) to censor App. Claudius Caecus introduced a series of reforms in 304 BC. [31] Their exact nature is uncertain, although he is thought to have begun the custom of publishing the calendar in advance of the month, depriving the priests of some of their power but allowing for a more consistent calendar for official business. [32]

Julian reform

Julius Caesar, following his victory in his civil war and in his role as pontifex maximus , ordered a reformation of the calendar in 46 BC. This was undertaken by a group of scholars apparently including the Alexandrian Sosigenes [33] and the Roman M. Flavius. [34] [29] Its main lines involved the insertion of ten additional days throughout the calendar and regular intercalation of a single leap day every fourth year in order to bring the Roman calendar into close agreement with the solar year. The year 46 BC was the last of the old system and included 3 intercalary months, the first inserted in February and two more—Intercalaris Prior and Posterior—before the kalends of December.

Later reforms

After Caesar's assassination, Mark Antony had Caesar's birth month Quintilis renamed July (Iulius) in his honor. After Antony's defeat at Actium, Augustus assumed control of Rome and, finding the priests had (owing to their inclusive counting) been intercalating every third year instead of every fourth, suspended the addition of leap days to the calendar for one or two decades until its proper position had been restored. See Julian calendar: Leap year error. In 8 BC, the plebiscite Lex Pacuvia de Mense Augusto renamed Sextilis August (Augustus) in his honor. [35] [36] [29] [lower-alpha 4]

In large part, this calendar continued unchanged under the Roman Empire. (Egyptians used the related Alexandrian calendar, which Augustus had adapted from their wandering ancient calendar to maintain its alignment with Rome's.) A few emperors altered the names of the months after themselves or their family, but such changes were abandoned by their successors. Diocletian began the 15-year indiction cycles beginning from the AD 297 census; [30] these became the required format for official dating under Justinian. Constantine formally established the 7-day week by making Sunday an official holiday in 321. Consular dating became obsolete following the abandonment of appointing nonimperial consuls in AD 541. [30] The Roman method of numbering the days of the month never became widespread in the Hellenized eastern provinces and was eventually abandoned by the Byzantine Empire in its calendar.


Roman dates were counted inclusively forward to the next one of three principal days within each month: [37]

These are thought to reflect a prehistoric lunar calendar, with the kalends proclaimed after the sighting of the first sliver of the new crescent moon a day or two after the new moon, the nones occurring on the day of the first-quarter moon, and the ides on the day of the full moon. The kalends of each month were sacred to Juno and the ides to Jupiter. [39] [40] The day before each was known as its eve (pridie); the day after each (postridie) was considered particularly unlucky.

The days of the month were expressed in early Latin using the ablative of time, denoting points in time, in the contracted form "the 6th December Kalends" (VI Kalendas Decembres). [38] In classical Latin, this use continued for the three principal days of the month [41] but other days were idiomatically expressed in the accusative case, which usually expressed a duration of time, and took the form "6th day before the December Kalends" (ante diem VI Kalendas Decembres). This anomaly may have followed the treatment of days in Greek, [42] reflecting the increasing use of such date phrases as an absolute phrase able to function as the object of another preposition, [38] or simply originated in a mistaken agreement of dies with the preposition ante once it moved to the beginning of the expression. [38] In late Latin, this idiom was sometimes abandoned in favor of again using the ablative of time.

The kalends were the day for payment of debts and the account books (kalendaria) kept for them gave English its word calendar . The public Roman calendars were the fasti , which designated the religious and legal character of each month's days. The Romans marked each day of such calendars with the letters: [43]

Each day was also marked by a letter from A to H to indicate its place within the nundinal cycle of market days.


A fragment of the Fasti Praenestini for the month of April (Aprilis), showing its nundinal letters on the left side Fasti Praenestini Massimo n2.jpg
A fragment of the Fasti Praenestini for the month of April ( Aprilis ), showing its nundinal letters on the left side

The nundinae were the market days which formed a kind of weekend in Rome, Italy, and some other parts of Roman territory. By Roman inclusive counting, they were reckoned as "ninth days" although they actually occurred every eighth day. Because the republican and Julian years were not evenly divisible into eight-day periods, Roman calendars included a column giving every day of the year a nundinal letter from A to H marking its place in the cycle of market days. Each year, the letter used for the markets would shift 2–5 letters along the cycle. As a day when the city swelled with rural plebeians, they were overseen by the aediles and took on an important role in Roman legislation, which was supposed to be announced for three nundinal weeks (between 17 and 24 days) in advance of its coming to a vote. The patricians and their clients sometimes exploited this fact as a kind of filibuster, since the tribunes of the plebs were required to wait another three-week period if their proposals could not receive a vote before dusk on the day they were introduced. Superstitions arose concerning the bad luck that followed a nundinae on the nones of a month or, later, on the first day of January. Intercalation was supposedly used to avoid such coincidences, even after the Julian reform of the calendar.

The 7-day week began to be observed in Italy in the early imperial period, [45] as practitioners and converts to eastern religions introduced Hellenistic and Babylonian astrology, the Jewish Saturday sabbath, and the Christian Lord's Day. The system was originally used for private worship and astrology but had replaced the nundinal week by the time Constantine made Sunday (dies Solis) an official day of rest in AD 321. The hebdomadal week was also reckoned as a cycle of letters from A to G; these were adapted for Christian use as the dominical letters.


The names of Roman months originally functioned as adjectives (e.g., the January kalends occur in the January month) before being treated as substantive nouns in their own right (e.g., the kalends of January occur in January). Some of their etymologies are well-established: January and March honor the gods Janus [46] and Mars; [47] July and August honor the dictator Julius Caesar [48] and his successor, the emperor Augustus; [49] and the months Quintilis, [50] Sextilis, [51] September, [52] October, [53] November, [54] and December [55] are archaic adjectives formed from the ordinal numbers from 5 to 10, their position in the calendar when it began around the spring equinox in March. [52] Others are uncertain. February may derive from the Februa festival or its eponymous februa ("purifications, expiatory offerings"), whose name may be either Sabine or preserve an archaic word for sulphuric. [56] April may relate to the Etruscan goddess Apru or the verb aperire ("to open").[ citation needed ] May and June may honor Maia [57] and Juno [58] or derive from archaic terms for "senior" and "junior". A few emperors attempted to add themselves to the calendar after Augustus, but without enduring success.

In classical Latin, the days of each month were usually reckoned as: [41]

31-day months [lower-alpha 7]
New Julian
31-day months [lower-alpha 8]
New Julian
30-day months [lower-alpha 9]
29-day months [lower-alpha 10]
1Kal.On the Kalends
Kal.Kal.Kal. Feb.
2a.d. VI Non.The 4th Day before the Nones
ante diem quartum Nonas
a.d. IV Non.a.d. IV Non.a.d. IV Non. Feb.
3a.d. V Non.The 3rd Day before the Nones
ante diem tertium Nonas
a.d. III Non.a.d. III Non.a.d. III Non. Feb.
4a.d. IV Non.On the Day before the Nones
Pridie Nonas
Prid. Non.Prid. Non.Prid. Non. Feb.
5a.d. III Non.On the Nones
Non.Non.Non. Feb.
6Prid. Non.The 8th Day before the Ides
ante diem octavum Idus
a.d. VIII Eid.a.d. VIII Eid.a.d. VIII Eid. Feb.
7Non.The 7th Day before the Ides
ante diem septimum Idus
a.d. VII Eid.a.d. VII Eid.a.d. VII Eid. Feb.
8a.d. VIII Eid.The 6th Day before the Ides
ante diem sextum Idus
a.d. VI Eid.a.d. VI Eid.a.d. VI Eid. Feb.
9a.d. VII Eid.The 5th Day before the Ides
ante diem quintum Idus
a.d. V Eid.a.d. V Eid.a.d. V Eid. Feb.
10a.d. VI Eid.The 4th Day before the Ides
ante diem quartum Idus
a.d. IV Eid.a.d. IV Eid.a.d. IV Eid. Feb.
11a.d. V Eid.The 3rd Day before the Ides
ante diem tertium Idus
a.d. III Eid.a.d. III Eid.a.d. III Eid. Feb.
12a.d. IV Eid.On the Day before the Ides
Pridie Idus
Prid. Eid.Prid. Eid.Prid. Eid. Feb.
13a.d. III Eid.On the Ides
Eid.Eid.Eid. Feb.
14Prid. Eid.The 19th Day before the Kalends
ante diem undevicesimum Kalendas
a.d. XVIII Kal.a.d. XVII Kal.a.d. XVI Kal. Mart.
15Eid.The 18th Day before the Kalends
ante diem duodevicesimum Kalendas
a.d. XVII Kal.a.d. XVI Kal.a.d. XV Kal. Mart.
16a.d. XVII Kal.The 17th Day before the Kalends
ante diem septimum decimum Kalendas
a.d. XVI Kal.a.d. XV Kal.a.d. XIV Kal. Mart.
17a.d. XVI Kal.The 16th Day before the Kalends
ante diem sextum decimum Kalendas
a.d. XV Kal.a.d. XIV Kal.a.d. XIII Kal. Mart.
18a.d. XV Kal.The 15th Day before the Kalends
ante diem quintum decimum Kalendas
a.d. XIV Kal.a.d. XIII Kal.a.d. XII Kal. Mart.
19a.d. XIV Kal.The 14th Day before the Kalends
ante diem quartum decimum Kalendas
a.d. XIII Kal.a.d. XII Kal.a.d. XI Kal. Mart.
20a.d. XIII Kal.The 13th Day before the Kalends
ante diem tertium decimum Kalendas
a.d. XII Kal.a.d. XI Kal.a.d. X Kal. Mart.
21a.d. XII Kal.The 12th Day before the Kalends
ante diem duodecimum Kalendas
a.d. XI Kal.a.d. X Kal.a.d. IX Kal. Mart.
22a.d. XI Kal.The 11th Day before the Kalends
ante diem undecimum Kalendas
a.d. X Kal.a.d. IX Kal.a.d. VIII Kal. Mart.
23a.d. X Kal.The 10th Day before the Kalends
ante diem decimum Kalendas
a.d. IX Kal.a.d. VIII Kal.a.d. VII Kal. Mart.
24a.d. IX Kal.The 9th Day before the Kalends
ante diem nonum Kalendas
a.d. VIII Kal.a.d. VII Kal.a.d. VI Kal. Mart. [lower-alpha 11]
25a.d. VIII Kal.The 8th Day before the Kalends
ante diem octavum Kalendas
a.d. VII Kal.a.d. VI Kal.a.d. V Kal. Mart.
26a.d. VII Kal.The 7th Day before the Kalends
ante diem septimum Kalendas
a.d. VI Kal.a.d. V Kal.a.d. IV Kal. Mart.
27a.d. VI Kal.The 6th Day before the Kalends
ante diem sextum Kalendas
a.d. V Kal.a.d. IV Kal.a.d. III Kal. Mart.
28a.d. V Kal.The 5th Day before the Kalends
ante diem quintum Kalendas
a.d. IV Kal.a.d. III Kal.Prid. Kal. Mart.
29a.d. IV Kal.The 4th Day before the Kalends
ante diem quartum Kalendas
a.d. III Kal.Prid. Kal.
30a.d. III Kal.The 3rd Day before the Kalends
ante diem tertium Kalendas
Prid. Kal.
31Prid. Kal.On the Day Before the Kalends
Pridie Kalendas

Dates after the ides count forward to the kalends of the next month and are expressed as such. For example, March 19 was expressed as "the 14th day before the April Kalends" (a.d. XIV Kal. Apr.), without a mention of March itself. The day after a kalends, nones, or ides was also often expressed as the "day after" (postridie) owing to their special status as particularly unlucky "black days".

The anomalous status of the new 31-day months under the Julian calendar was an effect of Caesar's desire to avoid affecting the festivals tied to the nones and ides of various months. However, because the dates at the ends of the month all counted forward to the next kalends, they were all shifted by one or two days by the change. This created confusion with regard to certain anniversaries. For instance, Augustus's birthday on the 23rd day of September was a.d. VIII Kal. Oct. in the old calendar but a.d. IX Kal. Oct. under the new system. The ambiguity caused honorary festivals to be held on either or both dates.


The Republican calendar only had 355 days, which meant that it would quickly unsynchronize from the solar year, causing, for example, agricultural festivals to occur out of season. The Roman solution to this problem was to periodically lengthen the calendar by adding extra days within February. February was broken into two parts, each with an odd number of days. The first part ended with the Terminalia on the 23rd (a.d. VII Kal. Mart.), which was considered the end of the religious year; the five remaining days beginning with the Regifugium on the 24th (a.d. VI Kal. Mart.) formed the second part; and the intercalary month Mercedonius was inserted between them. In such years, the days between the ides and the Regifugium were counted down to either the Intercalary Kalends or to the Terminalia. The intercalary month counted down to nones and ides on its 5th and 13th day in the manner of the other short months. The remaining days of the month counted down towards the March Kalends, so that the end of Mercedonius and the second part of February were indistinguishable to the Romans, one ending on a.d. VII Kal. Mart. and the other picking up at a.d. VI Kal. Mart. and bearing the normal festivals of such dates.

Apparently because of the confusion of these changes or uncertainty as to whether an intercalary month would be ordered, dates after the February ides are attested as sometimes counting down towards the Quirinalia (Feb. 17), the Feralia (Feb. 21), or Terminalia (Feb. 23) [59] rather than the intercalary or March kalends.

The third-century writer Censorinus says:

When it was thought necessary to add (every two years) an intercalary month of 22 or 23 days, so that the civil year should correspond to the natural (solar) year, this intercalation was in preference made in February, between Terminalia [23rd] and Regifugium [24th]. [60]

The fifth-century writer Macrobius says that the Romans intercalated 22 and 23 days in alternate years (Saturnalia, 1.13.12); the intercalation was placed after 23 February and the remaining five days of February followed (Saturnalia, 1.13.15). To avoid the nones falling on a nundine, where necessary an intercalary day was inserted "in the middle of the Terminalia, where they placed the intercalary month". [61]

This is historically correct. In 167 BC Intercalaris began on the day after 23 February [62] and in 170 BC it began on the second day after 23 February. [63] Varro, writing in the first century BC, says "the twelfth month was February, and when intercalations take place the five last days of this month are removed." [64] Since all the days after the Ides of Intercalaris were counted down to the beginning of March Intercalaris had either 27 days (making 377 for the year) or 28 (making 378 for the year).

There is another theory which says that in intercalary years February had 23 or 24 days and Intercalaris had 27. No date is offered for the Regifugium in 378-day years. [65] Macrobius describes a further refinement whereby, in one 8-year period within a 24-year cycle, there were only three intercalary years, each of 377 days. This refinement brings the calendar back in line with the seasons, and averages the length of the year to 365.25 days over 24 years.

The Pontifex Maximus determined when an intercalary month was to be inserted. On average, this happened in alternate years. The system of aligning the year through intercalary months broke down at least twice: the first time was during and after the Second Punic War. It led to the reform of the 191 BC Acilian Law on Intercalation, the details of which are unclear, but it appears to have successfully regulated intercalation for over a century. The second breakdown was in the middle of the first century BC and may have been related to the increasingly chaotic and adversarial nature of Roman politics at the time. The position of Pontifex Maximus was not a full-time job; it was held by a member of the Roman elite, who would almost invariably be involved in the machinations of Roman politics. Because the term of office of elected Roman magistrates was defined in terms of a Roman calendar year, a Pontifex Maximus would have reason to lengthen a year in which he or his allies were in power or shorten a year in which his political opponents held office.

Although there are many stories to interpret the intercalation, a period of 22 or 23 days is always ¾ synodic month. Obviously, the month beginning shifts forward (from the new moon, to the third quarter, to the full moon, to the first quarter, back the new moon) after intercalation.


A fragment of an imperial consular list Kalender.jpg
A fragment of an imperial consular list

As mentioned above, Rome's legendary 10-month calendar notionally lasted for 304 days but was usually thought to make up the rest of the solar year during an unorganized winter period. The unattested but almost certain lunar year and the pre-Julian civil year were 354 or 355 days long, with the difference from the solar year more or less corrected by an irregular intercalary month. The Julian year was 365 days long, with a leap day doubled in length every fourth year, almost equivalent to the present Gregorian system.

The calendar era before and under the Roman kings is uncertain but dating by regnal years was common in antiquity. Under the Roman Republic, from 509 BC, years were most commonly described in terms of their reigning ordinary consuls. [30] (Temporary and honorary consuls were sometimes elected or appointed but were not used in dating.) [30] Consular lists were displayed on the public calendars. After the institution of the Roman Empire, regnal dates based on the emperors' terms in office became more common. Some historians of the later republic and early imperial eras dated from the legendary founding of the city of Rome ( ab urbe condita or AVC). [30] Varro's date for this was 753 BC but other writers used different dates, varying by several decades.[ citation needed ] Such dating was, however, never widespread. After the consuls waned in importance, most Roman dating was regnal [67] or followed Diocletian's 15-year Indiction tax cycle. [30] These cycles were not distinguished, however, so that "year 2 of the indiction" may refer to any of 298, 313, 328, &c. [30] The Orthodox subjects of the Byzantine Empire used various Christian eras, including those based on Diocletian's persecutions, Christ's incarnation, and the supposed age of the world.

The Romans did not have records of their early calendars but, like modern historians, assumed the year originally began in March on the basis of the names of the months following June. The consul M. Fulvius Nobilior (r. 189 BC) wrote a commentary on the calendar at the Temple of Hercules Musarum that claimed January had been named for Janus because the god faced both ways, [68] [ where? ] suggesting it had been instituted as a first month.[ citation needed ] It was, however, usually said to have been instituted along with February, whose nature and festivals suggest it had originally been considered the last month of the year. The consuls' term of office—and thus the order of the years under the republic—seems to have changed several times. Their inaugurations were finally moved to 1 January (Kal. Ian.) in 153 BC to allow Q. Fulvius Nobilior to attack Segeda in Spain during the Celtiberian Wars, before which they had occurred on 15 March ( Eid. Mart.). [69] There is reason to believe the inauguration date had been 1 May during the 3rd century BC until 222 BC[ citation needed ] and Livy mentions earlier inaugurations on 15 May (Eid. Mai.), 1 July (Kal. Qui.), 1 August (Kal. Sex.), 1 October (Kal. Oct.), and 15 December (Eid. Dec.). [70] [ where? ] Under the Julian calendar, the year began on 1 January but years of the Indiction cycle began on 1 September.

In addition to Egypt's separate calendar, some provinces maintained their records using a local era. [30] Africa dated its records sequentially from 39 BC; [67] Spain from AD 38.[ citation needed ] This dating system continued as the Spanish era used in medieval Spain.[ citation needed ]

Conversion to Julian or Gregorian dates

The continuity of names from the Roman to the Gregorian calendar can lead to the mistaken belief that Roman dates correspond to Julian or Gregorian ones. In fact, the essentially complete list of Roman consuls allows general certainty of years back to the establishment of the republic but the uncertainty as to the end of lunar dating and the irregularity of Roman intercalation means that dates which can be independently verified are invariably weeks to months outside of their "proper" place. Two astronomical events dated by Livy show the calendar 4 months out of alignment with the Julian date in 190 BC and 2 months out of alignment in 168 BC. Thus, "the year of the consulship of Publius Cornelius Sciopio Africanus and Publius Licinius Crassus" (usually given as "205 BC") actually began on 15 March 205 BC and ended on 14 March 204 BC according to the Roman calendar but may have begun as early as November or December 206 BC owing to its misalignment. Even following the establishment of the Julian calendar, the leap years were not applied correctly by the Roman priests, meaning dates are a few days out of their "proper" place until a few decades into Augustus's reign.

Given the paucity of records regarding the state of the calendar and its intercalation, historians have reconstructed the correspondence of Roman dates to their Julian and Gregorian equivalents from disparate sources. There are detailed accounts of the decades leading up to the Julian reform, particularly the speeches and letters of Cicero, which permit an established chronology back to about 58 BC. The nundinal cycle and a few known synchronisms—e.g., a Roman date in terms of the Attic calendar and Olympiad—are used to generate contested chronologies back to the start of the First Punic War in 264 BC. Beyond that, dates are roughly known based on clues such as the dates of harvests and seasonal religious festivals.

See also


  1. That is, the 1st, 3rd, 5th, and 8th months prior to the introduction and repositioning of January and February.
  2. Plutarch reports this tradition while claiming that the months had more probably predated or originated with Romulus. [17] [18]
  3. This equivalence was first described by Stanyan in his history of ancient Greece. [23]
  4. There are some documents which state the month had been renamed as early as 26 or 23 BC, but the date of the Lex Pacuvia is certain.
  5. The NP days are sometimes thought to mark days when political and judicial activities were prohibited only until noon, standing for nefastus priore.
  6. The QRCF days are sometimes supposed, on the basis of the Fasti Viae Lanza which gives it as Q. Rex C. F., to stand for "Permissible when the King Has Entered the Comitium" (Quando Rex Comitiavit Fas). [44]
  7. The original 31-day months of the Roman calendar were March, May, Quintilis or July, and October.
  8. The 31-day months established by the Julian reform were January, Sextilis or August, and December. The other 31-day months of the Julian calendar continued to use the old system, with their Nones on the 7th and Ides on the 15th.
  9. The 30-day months established by the Julian reform were April, June, September, and November.
  10. The 29-day months of the calendar prior to the Julian reform were January, April, June, Sextilis, September, November, and December. After the Julian reform, February could have 29 days during a leap year but it was not reckoned according to this list until late in the imperial period. Instead, the sixth day before the March Kalends was initially treated as lasting for 48 hours.
  11. After the Julian reform, this day was reckoned to last 48 hours during a leap year.

Related Research Articles

Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both days and months.

A leap year is a calendar year containing an additional day added to keep the calendar year synchronized with the astronomical or seasonal year. Because seasons and astronomical events do not repeat in a whole number of days, calendars that have the same number of days in each year drift over time with respect to the event that the year is supposed to track. By inserting an additional day or month into the year, the drift can be corrected. A year that is not a leap year is called a common year.

Metonic cycle period of very close to 19 years that is nearly a common multiple of the solar year and the synodic (lunar) month

For astronomy and calendar studies, the Metonic cycle or Enneadecaeteris is a period of an almost exactly 19 years that is nearly a common multiple of the solar year and the synodic (lunar) month. The Greek astronomer Meton of Athens observed that a period of 19 years is almost exactly equal to 235 synodic months and, rounded to full days, counts 6,940 days. The difference between the two periods is only a few hours, depending on the definition of the year.

Quintilis original fifth month of the Roman calendar

In the ancient Roman calendar, Quintilis or Quinctilis was the month following Junius (June) and preceding Sextilis (August). Quintilis is Latin for "fifth": it was the fifth month in the earliest calendar attributed to Romulus, which began with Martius and had 10 months. After the calendar reform that produced a 12-month year, Quintilis became the seventh month, but retained its name. In 45 BC, Julius Caesar instituted a new calendar that corrected astronomical discrepancies in the old. After his death in 44 BC, the month of Quintilis, his birth month, was renamed Julius in his honor, hence July.

Sextilis original sixth month in the Roman calendar

Sextilis ("sixth") or mensis Sextilis was the Latin name for what was originally the sixth month in the Roman calendar, when March was the first of ten months in the year. After the calendar reform that produced a twelve-month year, Sextilis became the eighth month, but retained its name. It was renamed Augustus (August) in 8 BC in honor of the first Roman emperor, Augustus. Sextilis followed Quinctilis, which was renamed Julius (July) after Julius Caesar, and preceded September, which was originally the seventh month.

Mercedonius, also known as Mercedinus, Interkalaris or Intercalaris, was the intercalary month of the Roman calendar. The resulting leap year was either 377 or 378 days long. It theoretically occurred every two years, but was sometimes avoided or employed by the Roman pontiffs for political reasons regardless of the state of the solar year. Mercedonius was eliminated by Julius Caesar when he introduced the Julian calendar in 46 BC.

<i>Februarius</i> shortest month of the Roman calendar

Februarius or February, fully the "February month", was the shortest month of the Roman calendar. It was eventually placed second in order, preceded by Ianuarius ("January") and followed by Martius. In the oldest Roman calendar, which the Romans believed to have been instituted by their legendary founder Romulus, March was the first month, and the calendar year had only ten months in all. Ianuarius and Februarius were supposed to have been added by Numa Pompilius, the second king of Rome, originally at the end of the year. Julius Caesar decided in 46 BC to move the start of the calendar from the beginning of March to the beginning of January.

<i>Ianuarius</i> First month of ancient Roman calendar

Ianuarius, fully Mensis Ianuarius, was the first month of the ancient Roman calendar, from which the Julian and Gregorian month of January derived. It was followed by Februarius ("February"). In the calendars of the Roman Republic, Ianuarius had 29 days. Two days were added when the calendar was reformed under Julius Caesar in 45 BCE.

<i>Maius</i> original third month of the Roman calendar

Maius or mensis Maius (May) was the third month of the ancient Roman calendar, following Aprilis (April) and preceding Iunius (June). On the oldest Roman calendar that had begun with March, it was the third of ten months in the year. May had 31 days.

Terminalia boundary marker

Terminalia was an ancient Roman festival in honour of the god Terminus, who presided over boundaries. His statue was merely a stone or post stuck in the ground to distinguish between properties. His worship is said to have been instituted by Numa who ordered that every one should mark the boundaries of his landed property by stones to be consecrated to Jupiter Terminalis, and at which every year sacrifices were to be offered at the festival of the Terminalia. On the festival the two owners of adjacent property crowned the statue with garlands and raised a crude altar, on which they offered up some corn, honeycombs, and wine, and sacrificed a lamb or a suckling pig. They concluded with singing the praises of the god. The public festival in honour of this god was celebrated at the sixth milestone on the road towards Laurentum doubtless because this was originally the extent of the Roman territory in that direction.

<i>Martius</i> (month) first month of the ancient Roman year

Martius or mensis Martius ("March") was the first month of the ancient Roman year until possibly as late as 153 BC. After that time, it was the third month, following Februarius (February) and preceding Aprilis (April). Martius was one of the few Roman months named for a deity, Mars, who was regarded as an ancestor of the Roman people through his sons Romulus and Remus.

<i>Aprilis</i> original fourth month of the Roman calendar

Aprilis or mensis Aprilis (April) was the fourth month of the ancient Roman calendar, following Martius (March) and preceding Maius (May). On the oldest Roman calendar that had begun with March, Aprilis was the second of ten months in the year. April had 30 days on calendars of the Roman Republic, with a day added to the month during the reform in the mid-40s BC that produced the Julian calendar.

<i>Iunius</i> (month) month of the ancient Roman calendar

On the ancient Roman calendar, mensis Iunius or Iunius, also Junius (June), was the fourth month, following Maius (May). In the oldest calendar attributed by the Romans to Romulus, Iunius was the fourth month in a ten-month year that began with March (Martius, "Mars' month"). The month following June was thus called Quinctilis or Quintilis, the "fifth" month. Iunius had 29 days until a day was added during the Julian reform of the calendar in the mid-40s BC. The month that followed Iunius was renamed Iulius (July) in honour of Julius Caesar.

September (Roman month)

September or mensis September was originally the seventh of ten months on the ancient Roman calendar that began with March. It had 29 days. After the reforms that resulted in a 12-month year, September became the ninth month, but retained its name. September followed what was originally Sextilis, the "sixth" month, renamed Augustus in honor of the first Roman emperor, and preceded October, the "eighth" month that like September retained its numerical name contrary to its position on the calendar. A day was added to September in the mid-40s BC as part of the Julian calendar reform.

October or mensis October was the eighth of ten months on the oldest Roman calendar. It had 31 days. October followed September and preceded November. After the calendar reform that resulted in a 12-month year, October became the tenth month, but retained its numerical name, as did the other months from September to December.

November or mensis November was originally the ninth of ten months on the Roman calendar, following October and preceding December. It had 29 days. In the reform that resulted in a 12-month year, November became the eleventh month, but retained its name, as did the other months from September through December. A day was added to November during the Julian calendar reform in the mid-40s BC.

December or mensis December was originally the tenth month of the Roman calendar, following November and preceding Ianuarius. It had 29 days. When the calendar was reformed to create a 12-month year starting in Ianuarius, December became the twelfth month, but retained its name, as did the other numbered months from Quintilis (July) to December. Its length was increased to 31 days under the Julian calendar reform.

Fasti Antiates Maiores

The Fasti Antiates maiores are a painted wall-calendar from the late Roman Republic, the oldest archaeologically attested local Roman calendar and the only such calendar known from before the Julian calendar reforms. It was created between 67 and 55 BC and discovered in 1915 at Anzio, the ancient Antium, in a crypt next to the coast. It is now located in the Palazzo Massimo alle Terme in Rome, part of the Museo Nazionale Romano.



  1. Mommsen & al. (1864), pp.  216.
  2. 1 2 Macrobius, Book I, Ch. 12, §3.
  3. 1 2 Kaster (2011), p. 137.
  4. Mommsen & al. (1864), pp.  217.
  5. Censorinus, Macrobius, and Solinus, cited in Key.
  6. 1 2 3 Mommsen & al. (1864) , p.  218.
  7. Macrobius, Book I, Ch. 13, §20.
  8. Kaster (2011), p. 165.
  9. Macrobius, Book I, Ch. 12, §39.
  10. Kaster (2011), p. 155.
  11. Macrobius, Book I, Ch. 12, §§5 & 38.
  12. Kaster (2011), pp. 137 & 155.
  13. 1 2 Rüpke (2011) , p.  23.
  14. "April". Unabridged. Randomhouse Inc. Retrieved January 9, 2018.
  15. "May". Unabridged. Randomhouse Inc. Retrieved January 9, 2018.
  16. 1 2 Blackburn & al. (1999), p. 669.
  17. 1 2 3 4 5 Plutarch , Ch. 18.
  18. 1 2 3 4 5 Perrin (1914) , pp.  368 ff.
  19. 1 2 Mommsen & al. (1864) , p.  219.
  20. Macrobius, Book I, Ch. 12, §34.
  21. Kaster (2011), p. 153.
  22. Roberts (1905), Book I, Ch. 19, §6.
  23. Stanyan (1707), p.  330.
  24. 47.13 and 47.14: "[47.13] In the five hundred and ninety-eighth year after the founding of the city, the consuls began to enter upon their office on 1 January. [47.14] The cause of this change in the date of the elections was a rebellion in Hispania."
  25. Ovid, Book II.
  26. Kline (2004), Book II, Introduction.
  27. Fowler (1899), p. 5.
  28. Macrobius.
  29. 1 2 3 Kaster (2011).
  30. 1 2 3 4 5 6 7 8 9 Mathieson (2003) , p.  14.
  31. Michels (1949), p. 340.
  32. Lanfranchi (2013).
  33. Pliny, Book XVIII, Ch. 57.
  34. Macrobius, Book I, Ch. 14, §2.
  35. Rotondi (1912), p. 441.
  36. Macrobius, Book I, Ch. 12.
  37. 1 2 3 4 Beck (1838) , p.  175.
  38. 1 2 3 4 5 Beck (1838) , p.  176.
  39. Ovid, Book I, ll. 55–56.
  40. 1 2 Beck (1838) , p.  177.
  41. Smyth (1920), §§1582–1587.
  42. Scullard (1981), pp. 44–45.
  43. Rüpke (2011), pp. 26–27.
  44. Brind'Amour (1983), pp. 256–275.
  45. "January, n.", OED.
  46. "March, n.2", OED.
  47. "July, n.", OED.
  48. "August, n.", OED.
  49. "†quintile, n.2", OED.
  50. "sextile, adj. and n.", OED.
  51. 1 2 "September, n.", OED.
  52. "October, n.", OED.
  53. "November, n.", OED.
  54. "December, n.", OED.
  55. "February, n.", OED.
  56. "May, n.2", OED.
  57. "June, n.", OED.
  58. A 94  inscription.[ which? ]
  59. Censorinus, The Natal Day, 20.28, tr. William Maude, New York 1900, available at .
  60. Macrobius, Book I, Ch. 13, §16, 19.
  61. Livy 45.44.3.
  62. Livy 43.11.13.
  63. Varro, On the Latin language, 6.13, tr. Roland Kent, London 1938, available at .
  64. Michels (1967).
  65. Corpus Inscriptionum Latinarum I, CIL VI.
  66. 1 2 Mathieson (2003) , p.  15.
  67. Varro.
  68. Livy, Book XLVII.
  69. Livy.