Roman calendar

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.

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 (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.

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 remaining slightly longer than the solar year, the date of Easter shifted far enough away from the vernal equinox that Pope Gregory XIII ordered its adjustment in the 16th century.

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
Museo del Teatro Romano de Caesaraugusta.43
Another reproduction of the Fasti Antiates Maiores


Fasti Praenestini Massimo n1
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.

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.

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).[a][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]

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.[13]

Calendar of Romulus
English Latin Meaning Length
in days
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 Month 31
Sextilis Mensis Sextilis Sixth Month 30
September Mensis September Seventh Month 30
October Mensis October Eighth Month 31
November Mensis November Ninth Month 30
December Mensis December Tenth Month 30

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[b] 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. 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, as were the two new months of the calendar.[20][21][c] Most sources thought he had established intercalation with the rest of his calendar. 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.[d] 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
English Latin Meaning Length
in days
January Mensis Ianuarius Month of Janus 29
February Mensis Februarius Month of the Februa 28
Intercalary Month
Mensis Intercalaris
Month of Wages 23
March Mensis Martius Month of Mars 31
April Mensis Aprilis Uncertain 29
May Mensis Maius Uncertain 31
June Mensis Iunius Month of Juno 29
Quintilis Mensis Quintilis
Mensis Quinctilis[16]
Fifth Month 31
Sextilis Mensis Sextilis Sixth Month 29
September Mensis September Seventh Month 29
October Mensis October Eighth Month 31
November Mensis November Ninth Month 29
December Mensis December Tenth Month 29

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 to the pontifex maximus, 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 caused Sextilis to be renamed August (Augustus) in his honor.[35][36][29][e]

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]

  • Kalends (Kalendae or Kal.), the 1st day of each month[37]
  • Nones (Nonae or Non.), the 7th day of full months[38] and 5th day of hollow ones,[37] 8 days—"nine" by Roman reckoning—before the Ides in every month
  • Ides (Idus, variously Eid. or Id.), the 15th day of full months[38] and the 13th day of hollow ones,[37] a day less than the middle of each month

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] reflected 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]

  • F (fastus, "permissible") on days when it was legal to initiate action in the courts of civil law (dies fasti, "allowed days")
  • C (comitialis) on fasti days during which the Roman people could hold assemblies (dies comitalis)
  • N (nefastus) on days when political and judicial activities were prohibited (dies nefasti)
  • NP (uncertain)[f] on public holidays (feriae)
  • QRCF (uncertain)[g] on days when the "king" (rex sacrorum) could convene an assembly
  • EN (endotercissus, an archaic form of intercissus, "halved") on days when most political and religious activities were prohibited in the morning and evening due to sacrifices being prepared or offered but were acceptable for a period in the middle of the day

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


Fasti Praenestini Massimo n2
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"). 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]

Day Original
31-day months[h]
New Julian
31-day months[i]
New Julian
30-day months[j]
29-day months[k]
1 Kal. On the Kalends
Kal. Kal. Kal. Feb.
2 a.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.
3 a.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.
4 a.d. IV Non. On the Day before the Nones
Pridie Nonas
Prid. Non. Prid. Non. Prid. Non. Feb.
5 a.d. III Non. On the Nones
Non. Non. Non. Feb.
6 Prid. Non. The 8th Day before the Ides
ante diem octavum Idus
a.d. VIII Eid. a.d. VIII Eid. a.d. VIII Eid. Feb.
7 Non. The 7th Day before the Ides
ante diem septimum Idus
a.d. VII Eid. a.d. VII Eid. a.d. VII Eid. Feb.
8 a.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.
9 a.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.
10 a.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.
11 a.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.
12 a.d. IV Eid. On the Day before the Ides
Pridie Idus
Prid. Eid. Prid. Eid. Prid. Eid. Feb.
13 a.d. III Eid. On the Ides
Eid. Eid. Eid. Feb.
14 Prid. Eid. The 19th Day before the Kalends
ante diem undevicesimum Kalendas
a.d. XVIII Kal. a.d. XVII Kal. a.d. XVI Kal. Mart.
15 Eid. The 18th Day before the Kalends
ante diem duodevicesimum Kalendas
a.d. XVII Kal. a.d. XVI Kal. a.d. XV Kal. Mart.
16 a.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.
17 a.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.
18 a.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.
19 a.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.
20 a.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.
21 a.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.
22 a.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.
23 a.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.
24 a.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.[l]
25 a.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.
26 a.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.
27 a.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.
28 a.d. V Kal. The 5th Day before the Kalends
ante diem quintum Kalendas
a.d. IV Kal. a.d. III Kal. Prid. Kal. Mart.
29 a.d. IV Kal. The 4th Day before the Kalends
ante diem quartum Kalendas
a.d. III Kal. Prid. Kal.
30 a.d. III Kal. The 3rd Day before the Kalends
ante diem tertium Kalendas
Prid. Kal.
31 Prid. 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[66]

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. 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] suggesting it had been instituted as a first month. 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 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] 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. This dating system continued as the Spanish era used in medieval Spain.

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. ^ Censorinus, Macrobius, and Solinus, cited in Key.[5]
  2. ^ That is, the 1st, 3rd, 5th, and 8th months prior to the introduction and repositioning of January and February.
  3. ^ Plutarch reports this tradition while claiming that the months had more probably predated or originated with Romulus.[17][18]
  4. ^ This equivalence was first described by Stanyan in his history of ancient Greece.[23]
  5. ^ 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.
  6. ^ The NP days are sometimes thought to mark days when political and judicial activities were prohibited only until noon, standing for nefastus priore.
  7. ^ 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]
  8. ^ The original 31-day months of the Roman calendar were March, May, Quintilis or July, and October.
  9. ^ 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.
  10. ^ The 30-day months established by the Julian reform were April, June, September, and November.
  11. ^ 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.
  12. ^ After the Julian reform, this day was reckoned to last 48 hours during a leap year.



  1. ^ Mommsen & al. (1864), pp. 216.
  2. ^ a b Macrobius, Book I, Ch. 12, §3.
  3. ^ a b Kaster (2011), p. 137.
  4. ^ Mommsen & al. (1864), pp. 217.
  5. ^ Key (1875).
  6. ^ a b c 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. ^ a b Rüpke (2011), p. 23.
  14. ^ "April". Unabridged. Randomhouse Inc. Retrieved January 9, 2018.
  15. ^ "May". Unabridged. Randomhouse Inc. Retrieved January 9, 2018.
  16. ^ a b Blackburn & al. (1999), p. 669.
  17. ^ a b c d e Plutarch, Ch. 18.
  18. ^ a b c d e Perrin (1914), pp. 368 ff.
  19. ^ a b 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. ^ a b c Kaster (2011).
  30. ^ a b c d e f g h i Mathieson (2003), p. 14.
  31. ^ Michaels (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. ^ a b c d Beck (1838), p. 175.
  38. ^ a b c d e Beck (1838), p. 176.
  39. ^ Ovid, Book I, ll. 55–56.
  40. ^ a b 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. ^ a b "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.
  59. ^ Censorinus, The Natal Day, 20.28, tr. William Maude, New York 1900, available at [1].
  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 [2].
  64. ^ Michels (1967).
  65. ^ Corpus Inscriptionum Latinarum I, CIL VI.
  66. ^ a b Mathieson (2003), p. 15.
  67. ^ Varro.
  68. ^ Livy, Book XLVII.
  69. ^ Livy.


External links

399 BC

Year 399 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Tribunate of Augurinus, Longus, Priscus, Cicurinus, Rufus and Philo (or, less frequently, year 355 Ab urbe condita). The denomination 399 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

46 BC

Year 46 BC was the last year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Caesar and Lepidus (or, less frequently, year 708 Ab urbe condita). The denomination 46 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

This year marks the change from the pre-Julian Roman calendar to the Julian calendar. The Romans had to periodically add a leap month every few years to keep the calendar year in sync with the solar year but had missed a few with the chaos of the civil wars of the late republic. Julius Caesar added two extra leap months to recalibrate the calendar in preparation for his calendar reform, which went into effect in 45 BC. This year therefore had 445 days, and was nicknamed annus confusionis ("year of confusion").

470 BC

Year 470 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Potitus and Mamercus (or, less frequently, year 284 Ab urbe condita). The denomination 470 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

Ab urbe condita

Ab urbe condita (Latin pronunciation: [ab ˈʊrbɛ ˈkɔndɪtaː]), or Anno urbis conditæ (Latin pronunciation: [ˈannoː ˈʊrbɪs ˈkɔndɪtae̯]), often abbreviated as AUC in either case, is a convention that was used in antiquity and by classical historians to refer to a given year in Ancient Rome. Ab urbe condita literally means "from the founding of the City", while anno urbis conditæ means "in the year since the City's founding". Therefore, the traditional year of the foundation of Rome, 753 BC, would be written AUC 1, while AD 1 would be AUC 754. The foundation of the Empire in 27 BC would be AUC 727.

Usage of the term was more common during the Renaissance, when editors sometimes added AUC to Roman manuscripts they published, giving the false impression that the convention was commonly used in antiquity. In reality, the dominant method of identifying years in Roman times was to name the two consuls who held office that year. In late antiquity, regnal years were also in use, as was the Diocletian era in Roman Egypt after AD 293, and in the Byzantine Empire after AD 537, following a decree by Justinian.


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 (often paper) 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.

Periods in a calendar (such as years and months) are usually, though not necessarily, synchronised with the cycle of the sun or the moon. The most common type of pre-modern calendar was the lunisolar calendar, a lunar calendar that occasionally adds one intercalary month to remain synchronised with the solar year over the long term.

The term calendar is taken from calendae, the term for the first day of the month in the Roman calendar, related to the verb calare "to call out", referring to the "calling" of the new moon when it was first seen.

Latin calendarium meant "account book, register" (as accounts were settled and debts were collected on the calends of each month). The Latin term was adopted in Old French as calendier and from there in Middle English as calender by the 13th century (the spelling calendar is early modern). A calendar can be on paper or electronic device.


The calends or kalends (Latin: kalendae) is the first day of every month in the Roman calendar. The English word calendar is derived from this word.

Dedication of the Basilica of St Mary Major

The Dedication of the Basilica of St Mary Major (In Dedicatione basilicae S. Mariae) is a feast day in the General Roman Calendar, optionally celebrated annually on 5 August with the rank of memorial.

In earlier editions of the General Roman Calendar, down to that of 1960, it is called the Dedication of the Basilica of St Mary of the Snows (In Dedicatione basilicae S. Mariae ad Nives), a reference to the legendary story about the foundation of the basilica. For the same reason the feast is also known popularly as Our Lady of the Snows. The reference to the legend was removed in the 1969 revision of the General Roman Calendar.


In ancient Rome, the fasti (Latin plural) were chronological or calendar-based lists, or other diachronic records or plans of official and religiously sanctioned events. After Rome's decline, the word fasti continued to be used for similar records in Christian Europe and later Western culture.

Public business, including the official business of the Roman state, had to be transacted on dies fasti, "allowed days". The fasti were the records of this business. In addition to the word's general sense, there were fasti that recorded specific kinds of events, such as the fasti triumphales, lists of triumphs celebrated by Roman generals. The divisions of time used in the fasti were based on the Roman calendar.

The yearly records of the fasti encouraged the writing of history in the form of chronological annales, "annals," which in turn influenced the development of Roman historiography.

Fasti (poem)

The Fasti or Fausti (Latin: Fastorum Libri Sex, "Six Books of the Calendar"), sometimes translated as The Book of Days or On the Roman Calendar, is a six-book Latin poem written by the Roman poet Ovid and published in 8 AD. Ovid is believed to have left the Fasti incomplete when he was exiled to Tomis by the emperor Augustus in 8 AD. Written in elegiac couplets and drawing on conventions of Greek and Latin didactic poetry, the Fasti is structured as a series of eye-witness reports and interviews by the first-person vates ("poet-prophet" or "bard") with Roman deities, who explain the origins of Roman holidays and associated customs—often with multiple aetiologies. The poem is a significant, and in some cases unique, source of fact in studies of religion in ancient Rome; and the influential anthropologist and ritualist J.G. Frazer translated and annotated the work for the Loeb Classical Library series. Each book covers one month, January through June, of the Roman calendar, and was written several years after Julius Caesar replaced the old system of Roman time-keeping with what would come to be known as the Julian calendar.

The popularity and reputation of the Fasti has fluctuated more than that of any of Ovid's other works. The poem was widely read in the 15th–18th centuries, and influenced a number of mythological paintings in the tradition of Western art. However, as scholar Carole E. Newlands has observed, throughout the 20th century "anthropologists and students of Roman religion … found it full of errors, an inadequate and unreliable source for Roman cultic practice and belief. Literary critics have generally regarded the Fasti as an artistic failure." In the late 1980s, however, the poem enjoyed a revival of scholarly interest and a subsequent reappraisal; it is now regarded as one of Ovid's major works, and has been published in several new English translations. Ovid was exiled from Rome for his subversive treatment of Augustus, yet the Fasti continues this treatment—which has led to the emergence of an argument in academia for treating the Fasti as a politically weighted work.

General Roman Calendar

For historical forms of the General Roman Calendar, see Tridentine Calendar, General Roman Calendar of 1954, General Roman Calendar of Pope Pius XII, General Roman Calendar of 1960, and General Roman Calendar of 1969.The General Roman Calendar is the liturgical calendar that indicates the dates of celebrations of saints and mysteries of the Lord (Jesus Christ) in the Roman Rite, wherever this liturgical rite is in use. These celebrations are a fixed annual date; or occur on a particular day of the week (examples are the Baptism of the Lord in January and the Feast of Christ the King in November); or relate to the date of Easter (examples are the celebrations of the Sacred Heart of Jesus and the Immaculate Heart of Mary). National and diocesan liturgical calendars, including that of the diocese of Rome itself as well as the calendars of religious institutes and even of continents, add other saints and mysteries or transfer the celebration of a particular saint or mystery from the date assigned in the General Calendar to another date.

These liturgical calendars also indicate the degree or rank of each celebration: Memorial (which can be merely optional), Feast, or Solemnity. Among other differences, the Gloria is said or sung at the Mass of a Feast but not at that of a Memorial, and the Creed is added on Solemnities.

The last general revision of the General Roman Calendar was in 1969 and was authorized by the motu proprio Mysterii Paschalis of Pope Paul VI. The motu proprio and the decree of promulgation were included in the book Calendarium Romanum, published in the same year by Libreria Editrice Vaticana. This contained also the official document Universal Norms on the Liturgical Year and the Calendar, and the list of celebrations of the General Roman Calendar. Both these documents are also printed (in their present revised form) in the Roman Missal, after the General Instruction of the Roman Missal. The 1969 book also provided a detailed unofficial commentary on that year's revision of the calendar.

The contents of the General Roman Calendar and the names in English of the celebrations included in it are here indicated in the official English version of the Roman Missal.

General Roman Calendar of 1954

This article lists the feast days of the General Roman Calendar as they were at the end of 1954. It is essentially the same calendar established by Pope Pius X (1903–1914) following his liturgical reforms, but it also incorporates changes that were made by Pope Pius XI (1922–1939), such as the institution of the Feast of Christ the King, and the changes made by Pope Pius XII (1939–1958) prior to 1955, chief among them the imposition of the Feast of the Immaculate Heart of Mary upon the universal Church (August 22, on the existing octave day of the Assumption) in 1944, the inscription of Pius X into the General Calendar (September 3) following his 1954 canonization, and the institution of the Feast of the Queenship of Mary (May 31) in October 1954.

The changes that the latter Pope made in 1955 are indicated in General Roman Calendar of Pope Pius XII. They included: a revision of the Church's traditional ranking of liturgical days; the institution of the feast of St. Joseph the Worker on May 1 as a Double of the I Class, requiring the transfer of Ss. Philip and James to May 11; the suppression of the Solemnity of Saint Joseph, which for just over a century had been celebrated on the second Wednesday after the Octave of Easter. A total of fifteen Octaves—all those except Easter, Pentecost, and Christmas—were also suppressed in the reform of 1955, as were most vigils (specifically, the vigils of all apostles save for that of Ss. Peter and Paul, and the vigils of the Immaculate Conception, Epiphany, and All Saints).

Five years later, Pope John XXIII made a further revision with the motu proprio Rubricarum instructum of July 23, 1960. This revision, the General Roman Calendar of 1960, was incorporated in the Roman Missal of 1962, which was issued as implementation of this motu proprio The 1960 calendar is thus the calendar approved by Pope Benedict XVI with his July 7, 2007 document Summorum Pontificum for use as an extraordinary form of the Roman Rite.

The General Roman Calendar was again revised in 1969, in connection with the revision of the Roman Missal, and later. For its current state, see General Roman Calendar.

For most of the celebrations here listed, the Mass is found in the Roman Missal of the time in the section called the "Proper of the Saints", but for those occurring from 24 December to 13 January it is found in the "Proper of the Season", as these days do not move with respect to the seasons of the Church year. The Offices of these feasts are likewise arranged in the Breviary.

While the General Calendar of 1954 is generally not authorized for liturgical use by traditional groups in communion with the Holy See, some sedevacantists continue to use it, as their members consider it to be the last calendar untainted by the revisions that began in 1955. Indults have been granted, however, to certain communities in full communion with Rome, such as some apostolates of the Institute of Christ the King Sovereign Priest.

General Roman Calendar of 1960

This article lists the feast days of the General Roman Calendar as reformed on 23 July 1960 by Pope John XXIII's motu proprio Rubricarum instructum. This 1960 calendar was incorporated into the 1962 edition of the Roman Missal, continued use of which Pope Benedict XVI authorized in his 7 July 2007 motu proprio Summorum Pontificum as an "extraordinary form of the Roman Rite".

Rubricarum instructum replaced the former classifications of Doubles, Semidoubles, and Simples with I, II, and III class feasts and commemorations. It removed a few feasts, in particular duplications such as the Feast of the Cross (3 May and 14 September), the Chair of Peter (18 January and 22 February), Saint Peter (1 August and 29 June), Saint John the Evangelist (6 May and 27 December), Saint Michael (8 May and 29 September), and Saint Stephen (3 August and 26 December).

This calendar is distinct from the General Roman Calendar of 1954 in that it also incorporates the changes made by Pope Pius XII in 1955, which included the reduction of octaves to three only, those of Christmas, Easter and Pentecost. See General Roman Calendar of Pope Pius XII.

General Roman Calendar of Pope Pius XII

In 1955 Pope Pius XII made several changes to the General Roman Calendar of 1954, changes that remained in force only until 1960, when Pope John XXIII, on the basis of further recommendations of the commission that Pius XII had set up, decreed a further revision of the General Roman Calendar (see General Roman Calendar of 1960). The changes made by Pope Pius XII thus remained unaltered for only five years.

He made the following changes by the decree "Cum nostra hac aetate" (De rubricis ad simpliciorem formam redigendis) of 23 March 1955

Ides of March

The Ides of March (; Latin: Idus Martiae, Late Latin: Idus Martii) was a day in the Roman calendar that corresponds to 15 March. It was marked by several religious observances and was notable for the Romans as a deadline for settling debts. In 44 BC, it became notorious as the date of the assassination of Julius Caesar which made the Ides of March a turning point in Roman history.

Julian calendar

The Julian calendar, proposed by Julius Caesar in 46 BC (708 AUC), was a reform of the Roman calendar. It took effect on 1 January 45 BC (709 AUC), by edict. It was the predominant calendar in the Roman world, most of Europe, and in European settlements in the Americas and elsewhere, until it was refined and gradually replaced by the Gregorian calendar, promulgated in 1582 by Pope Gregory XIII.

The Julian calendar is still used in parts of the Eastern Orthodox Church, in parts of Oriental Orthodoxy and Anabaptism, as well as by the Berbers.

During the 20th and 21st centuries, the date according to the Julian calendar is 13 days behind the Gregorian date, and after the year 2100 will be one day more.

Mysterii Paschalis

Mysterii Paschalis is an apostolic letter issued motu proprio (that is, "of his own accord") by Pope Paul VI on 14 February 1969. It reorganized the liturgical year of the Roman Rite and revised the liturgical celebrations of Jesus Christ and the saints in the General Roman Calendar.


November is the eleventh and penultimate month of the year in the Julian and Gregorian Calendars, the fourth and last of four months to have a length of 30 days and the fifth and last of five months to have a length of less than 31 days. November was the ninth month of the ancient Roman calendar. November retained its name (from the Latin novem meaning "nine") when January and February were added to the Roman calendar.

November is a month of late spring in the Southern Hemisphere and late autumn in the Northern Hemisphere. Therefore, November in the Southern Hemisphere is the seasonal equivalent of May in the Northern Hemisphere and vice versa. In Ancient Rome, Ludi Plebeii was held from November 4–17, Epulum Jovis was held on November 13 and Brumalia celebrations began on November 24. These dates do not correspond to the modern Gregorian calendar.

November was referred to as Blōtmōnaþ by the Anglo-Saxons. Brumaire and Frimaire were the months on which November fell in the French Republican 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).The nundinal cycle, market week, or 8-day week (Latin: nundinum or internundinum) was the cycle of days preceding and including each nundinae. These were marked on fasti using nundinal letters from A to H. The earliest form of the Roman calendar is sometimes said to have included exactly 38 such cycles, running for 304 days from March to December before an unorganized expanse of about 50 winter days. The lengths of the Republican and Julian calendars, however, were not evenly divisible by 8; under these systems, the nundinae fell on a different letter each year. These letters formed the basis of the later Christian dominical letters.

Tridentine Calendar

The Tridentine Calendar is the calendar of saints to be honoured in the course of the liturgical year in the official liturgy of the Roman Rite as reformed by Pope Pius V, implementing a decision of the Council of Trent, which entrusted the task to the Pope.

The text of the Tridentine Calendar can be found in the original editions of the Tridentine Roman Breviary and of the Tridentine Roman Missal.Use of both these texts, which included Pius V's revised calendar, was made obligatory throughout the Latin Rite except where other texts of at least two centuries' antiquity were in use, and departures from it were not allowed. The Apostolic Constitution Quod a nobis, which imposed use of the Tridentine Roman Breviary, and the corresponding Apostolic Constitution Quo primum concerning the Tridentine Roman Missal both decreed: "No one whosoever is permitted to alter this letter or heedlessly to venture to go contrary to this notice of Our permission, statute, ordinance, command, precept, grant, indult, declaration, will, decree and prohibition. Should anyone, however, presume to commit such an act, he should know that he will incur the wrath of Almighty God and of the Blessed Apostles Peter and Paul." See the article on Quo primum.

Pius V himself altered his Calendar when, after the victory in 1571 of the battle of Lepanto, he added the feast of Our Lady of Victory. In 1585, Pope Sixtus V restored the feast of the Presentation of the Virgin Mary, which Pope Pius V had removed. See, below, "Some differences in relation to later editions of the Roman calendar".

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