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date: 29 June 2022

calendar, Romanfree

calendar, Romanfree

  • Jörg Rüpke


The Roman calendar developed from a group of Italian luni-solar calendars into a purely solar calendar at the end of the 4th century bce in the context of a political and juridical codification. The resulting graphic form of the fasti was unique in its documentation of all the days of the year. At Rome, it served as a frame for religious and historical data. The complex form of intercalation was reduced by C. Iulius Caesar to a single day, fixing new length of months and establishing a stable relationship with astronomic phenomena. In this shape, and stripped from its urban contents to a technical and emperor-related instrument, it served as a universal point of reference, into which all local calendars made themselves translatable. Despite its many religious associations, it thus survived into Christian Late Antiquity and into today’s widespread “Gregorian calendar.”


  • Roman Myth and Religion

Updated in this version

Text expanded to reflect current scholarship. Primary sources added.

A calendar is a form of organising time, above all of dividing the year into subunits of months and weeks, and of classifying days. The Romans had no corresponding concept; describing such a form of time-reckoning as well as social coordination, they would have used the term annus Romanus, which above all addressed the names of the months and methods of intercalation and ignored the medial form. However, the presence in everyday life of such technical regulations and the imagination of such a year would have been determined by its most important written and graphic form, the fasti (usually translated as calendar, too). The calendar variety that is called “Roman” in this article is the dominating form, used for political, juridical, and military purposes. More simple forms and many different regional varieties co-existed. At least in the imperial period, however, the fasti was so dominant that competing calendars from towns around Rome were reduced to antiquarian memory; even Greek-speaking Jews (and later Christians) overwhelmingly used this way of dating and coordinating activities. As an instrument of the Roman administration, the military and, to some extent, Roman merchants, the local calendar of the city of Rome was used as a first or second calendar across the Empire. Even at Rome, however, references to the first (or last) visibility of stars at dusk or at dawn, horoscopes, and indications of lunar phases attest to the ongoing employment of different devices for annual time-reckoning, techniques that also left traces in the written form of the Roman calendar, the fasti.

Like most calendars of the Mediterranean world of the 1st millennium bce, Romans tried to integrate a more or less precise indication of the solar year (arriving at 366 instead of 365.2422 days), a period with implications for navigation, agricultural, and other seasonal activities, with the usage of the lunar periods of roughly 29.53 days, in many cultures translated into months of 29 or 30 days, but at Rome, 29 and 31 days. Long-term Babylonian observations and Greek mathematics respectively offered models for a coherent integration by way of regular intercalation of (lunar) months in cycles of 8 or 19 years. At Rome, however (as in many Greek cities: see calendar, Greek), actual practices and decisions about intercalations were informed by traditions and practicalities rather than mathematics. Nevertheless, the growing preference for stable sub-units of months, which were defined by conventions rather than empirical observation, leading to first loosing track of lunar phases and finally reducing intercalation to a single day, characterises the history of the Roman calendar.

The 5th century bce Etruscan festival list of the tabula Capuana indicates a system of lunar intervals parallel to the Roman institution of the idus and kalendae, the full moon day and the first day of the months.1 But the changes of the Roman calendar of the middle republic, described below, were not reflected in later Etruscan documents. The liber linteus, a strip of linen containing an Etruscan sacrificial calendar from the 2nd century bce, indicates several dates of a calendar that numbered the dates of the month from one to thirty, perhaps a still soli-lunar calendar.2 A probably Etruscan date could still be used by 67 bce (ILLRP 589). With regard to Latin calendars, an inscription of the year 58 bce adds the dating mense Flus are to a Roman date of a specific day (ILLRP 508). Thus it is difficult to decide whether the differences might have been reduced to different names of the months within an identical system of reckoning (a phenomenon widespread in the Eastern Mediterranean). The same holds true for the information given by Suetonius in his biography of Augustus that some Italian civitates made the day of Augustus’ first visit to them the beginning of the year (Suet. Aug. 59).

Historical Development

The earliest reliable source for a specific calendar at Rome is Varro’s dating of a law of the early 5th century bce mentioning an intercalary month (Macrob. Sat. 1.13.21). This presupposes a practice of intercalating a full (lunar) month at a fixed place in the series of months, most probably (as in later practice) and astonishingly (see below) not at the end, but shortly before the end of February. The numbering of months (Quinctilis, Sextilis . . . December) must belong to this system. Speculations about an earlier system of ten months, articulated in the late republican period (Cens. 20.2; Ov. fast. 1.27–44), seem to have been inventions designed to credit the cultural hero Numa also with calendrical innovations. Late republican authors imagined some sort of codification of the calendrical system already by the Decemviri in the 5th century bce, but historical texts suggest that it was only at the end of the 4th century bce that a calendar was fixed in writing.3 The previous calendar was characterised by a sequence of three periods of eight days. The first started from the nonae (first quarter of the moon), the second from the (e)idus (full moon), the third started from the eighth (or “ninth,” according to Roman inclusive counting) day after the ides, reaching up to the kalendae. This latter day took its name from its ritual feature. Based on the observation of the new moon the number of the days to the next nonae were publicly “called out” (kalare; Varro, ling. 6.27; Macrob. Sat. 1.15.10). Occasional intercalation of a month brought the year into alignment with the solar year.

Fixing the calendar in writing entailed the stabilisation of the number of days throughout the month and enabled the introduction of countable, precise periods or periodicities for legal or other business—for example, an uninterrupted weekly recurrence (nundinae, allowing for a market every eight days, or “30 days”).4 The months were given 31 (January, March, May, Quinctilis, October), 28 (February) or 29 days, 355 in total. The mensis intercalaris (intercalated month) of 27 days (graphically represented as a 13th column in the painted Fasti Antiates maiores) replaced consecutively the last 5 or 4 days of February and resulted in a net intercalation of 22 or 23 days every second year, adding up to an average of 366.25 days. Intercalation, however, was subject to arbitrary decision by the pontifical college, which could result in discrepancies with the solar year of up to several months.5 Seemingly lunar, the Roman calendar was in fact a pure solar one, even if a faulty one.

C. Iulius Caesar used his unique power position as a dictator (and also pontifex maximus) to lengthen the months of 29 days to 30 or 31 (Sextilis, December) and thereby reduce the intercalary period to just 1 day by doubling the 24th February (bisextilis; sources: Plin. NH 18.211–212; Suet. Iul. 40; Cens. 20.6–11; Dio 43.26; Macrob. Sat. 1.14), a day not represented in the written for of the calendars.6 A solitary lengthening of the year 46 bce to 445 days brought the revised calendar in an intended alignment with the solar year (e.g., 25 December as winter solstice). A misunderstanding of the rule for intercalation (every three instead of four years) was corrected by Augustus in 8 bce (Macrob. Sat. 1.14.13–15). This “Iulian” calendar was used in Europe and European colonies until its gradual replacement by Gregory XIII’s Gregorian calendar after 1582 and in particular 1700 (England: 1752) or Orthodox calendars as reformed in the early 20th century ce, not changed in the length of the months, but only in the rule-based dropping of intercalations and the cutting out of days in the moments of reform.

Graphic Representation

The written calendar, first represented in graphic form in around 300 bce, and associated in Roman memory with the aedile and pontifical scribe Gnaeus Flavius (Livy 9.46; Val. Max. 2.5.2; Macrob. Sat. 1.15.9), attributed specific characteristics to nearly every day.7 It is probable that this reform was instigated by the pontiff and censor Ap. Claudius Caecus. In the extant fasti, the characters attributed to each of the individual days are fas (days for crucial legal actions) and its semantic opposite nefas (with various distinctions of detail) and dies comitiales. (days for assemblies). In practice, the latter also functioned as days, on which cases could be initiated before the praetor, differing from dies fasti only by the fact that, on days marked with a C, the magistrates could also summon comitia, decision-making people’s assemblies (Varro, Ling. 6.29–32; Ov. Fast. 1.45–54; Inscr. It. 13.2.111–113 (fast. Praen.); Macrob. Sat. 1.16.13–14). This minor differentiation was a result of developments at the beginning of the 3rd century bce (287 bce, lex Hortensia), clarifying that plebeian assemblies (concilia plebis) were not as narrowly restricted.8

Thus, the calendar’s pervading function was to attribute a religious qualification to all, even political or juridical actions. The label nefas prohibited the presentation of a case before the praetor in legis actiones, and the interaction between state apparatus and citizen (cum populo agere). The religious character of the nefas designation becomes clear in the sanction of piaculum, added as NP to a smaller number of days. This term applied equally to the offence (piaculum est) and the “expiatory sacrifice” it gave rise to (piaculum facere). All in all, this regulation of political activity was a systematisation of existing practices, the major concern was to the days on which comitia were held. The existing practices that had to be taken into account widely varied. Some days were genuinely sacrosanct days or feriae (marked as NP), others were, for instance, “magistrates” holidays’ (marked N). All such details were flattened by the massive condensation of information, reflected and sharpened by the abbreviation of the wording, a technique just developing in Roman inscriptions (ILLRP 16–17).

The resulting graphic organisation was basically stable from the earliest attested individual copy, a painted wall calendar in the temple of Hercules Musarum, around 170 bce, faithfully reproduced by the Fasti Antiates to late ancient copies in the form of codices, dedicating a full page to each month.9 Each month is made up by several columns of information. At the left margin, there was the column of recurring letters from A to H. These were the litterae nundinales, which indicated the cycle of a week of eight days. Already in Augustan times a parallel column for a planetary week of seven days was added in some copies for astrological usage.10 In the 4th century ce, thus, a smooth transition to the latter form of the week was possible.

The second column was formed by KAL, NON, and EID on the relevant days (1st, 5/7th, 13/15th in the old months of 31 days) and often numbers indicating the distance to the next these days, the Roman way of dating. The third column, realised nearly every day, indicates the legal, indirectly the religious status of the day as explained above. A fourth column (or rather class) of information fills in with smaller letters a lot of the space left, including information on games (ludi) and related merkati (fairs), more frequently on dies natales, on founding days of temples. “On this day, a temple had been dedicated to Mars in the Campus” —would be a standard rendering for an abbreviated Marti in Campo or the like. The latter always refer to the founding of temples in Rome. In several cases these “birthdays” of temples, celebrated at specific locations and full of memories, frequently of Roman military victories and divine support, became occasions of public communication or even popular festivals. In the course of Late Antiquity many dies natales of Christian martyrs competed for attention and finally dominated medieval calendars.11 From the immediate post-Caesarian period onwards a new type of holiday is established by the senate on behalf of the celebration of imperial victories, births, or their accession to power (feriae ex senatus consulto, quod eo die . . .). Intensified by games and above all races, such imperial festivals were the backbone of the Roman year as experienced by many.

Geographical Reach

The contents of the graphic calendars nearly always refer to Roman events and rituals. The only exception is a single date in the exceptional and learned fasti from Praeneste.12 The fasti were never used to add local, Italian festivals or cultic events. Throughout the empire, however, holidays (feriae) referring to events related to the emperor or his family were made obligatory days, on which legal procedures were suspended (Flavian municipal law c. 92 = Lex Irnitana 10 B 25–51). Typically, such dates had been made part of local calendars. The urban character of the Roman calendar is reflected in the geographical distribution of the known copies. Of the more than fifty fragments of fasti found so far, about one-half has been found in or could be attributed to the city of Rome, while most of the remaining ones belong to Latium, Etruria, and Campania. The so-called “Fasti Guidizzolenses” (Inscr. It. 13.2.234) belong to the surroundings of Brixia and are the northernmost item; the southernmost item, the Fasti Tauromenitani, belongs to Tauromenium, an Augustan colony in Sicily.13 This last one is the only copy found outside the peninsula of Italy. Both demonstrate visible irregularities. Around Brixia, the calendar displayed Roman months and their length, but neglected all further information apart from a small list of dated festivals. The Sicilian specimen implies that the popular calendar used was a Greek luni-solar one.14

Typically, the impact of the Roman calendar was diverse as can be seen in the province of Asia. In 9 bce, a calendar reform replaced the former lunisolar calendar by a Julian-type calendar with traditional Macedonian names of the months and a new year’s day on the birthday of Augustus (September 23). Details show the careful accommodation to local cultural practices: Months of 31 days, required by the Julian calendar, had not been used by conventional lunar months before; therefore the numbering was adapted to 29, “30a” and “30b.”15 The decree was published by the proconsular governor but would have been built on the consensus of local elites. Nevertheless, many eastern cities and areas, even within the province of Asia minor, continued to employ their old luni-solar systems. If a synchronism was needed, hemerologia—synopses or lists displaying various lists of dates side by side and thus synchronizing themwere at hand.16 The impact of the Roman calendar was more direct in the Roman army. In the Eastern Mesopotamian border region, the garrison at Dura Europos employed a Roman calendar, as demonstrated by the Roman dates of their feriale, their list of festivals from the early 3rd century ce preserved on papyrus.17 Here, many urban dates led to obligatory rituals by the military, and imperial dates, even back to the first emperors, featured prominently.

As far as the length of the year and the adapted structure of just twelve months of the Julian calendar is concerned, the technical shape was an instrument suitable for an empire.18 Judging from dated inscriptions, the technical system of the Roman calendar was adapted in Italy and many parts, especially of the Western Empire during the 2nd and 3rd century ce.19 Outside of the imperialist apparatus, further details were lost outside of the Italian peninsula. The difference to the urban situation is clear-cut. Whereas in the latter, one’s own calendar is not only an instrument to represent astronomic facts for practical purposes and to coordinate social activities, but also serving as a historical memory; in the space of the empire is a representation of the time of the imperial overlord, into which local calendars need to be translatable.20

Primary Texts


  • Belfiore, Valentina. Il Liber linteus di Zagabria: Testualità e contenuto. Biblioteca di Studi etruschi. Pisa, Italy: Serra, 2010.
  • Ben-Dov, Jonathan, and Lutz Doering, eds. The Construction of Time in Antiquity: Ritual, Art and Identity. Cambridge, UK: Cambridge University Press, 2017.
  • Bennett, Chris. “The Early Augustan Calendars in Rome and Egypt.” Zeitschrift für Papyrologie und Epigraphik 142 (2003):221–240.
  • Brind’Amour, Pierre. Le calendrier romain: Recherches chronologiques, Collection d'études anciennes de l'Université d'Ottawa 2. Ottawa, ON: Éditions de l'Université d'Ottawa, 1983.
  • Cristofani, Mauro. Tabula Capuana: Un calendario festivo di età arcaica. Istituto nazionale di studi etruschi e italici: biblioteca di Studi Etruschi 29. Florence: Olschki, 1995.
  • Degrassi, Attilio. “Epigraphica III: 7. Sul nuovo calendario romano di Tauromenium.” Memorie Accademia Nazionale dei Lincei, cl. mor. ser. 8, no. 13 (1967): 27–29.
  • Feeney, Denis. Caesar's Calendar: Ancient Time and the Beginnings of History. Sather Classical Lectures. Berkeley: University of California Press, 2007.
  • Fink, Robert O., Allan S. Hoey, and Walter F. Snyder. 'The Feriale Duranum.' Yale Classical Studies 7 (1940): 1-222.
  • Fishwick, Duncan. “Dated Inscriptions and the Feriale Duranum.” Syria 65, no. 3–4 (1988.): 349–361.
  • Herz, Peter. Untersuchungen zum Festkalender der römischen Kaiserzeit nach datierten Weih-und Ehreninschriften. Vol. 2 Bde. Bonn, Germany: Habelt, 1975.
  • Hölkeskamp, Karl-Joachim. “Die Entstehung der Nobilität und der Funktionswandel des Volkstribunats: Die historische Bedeutung der lex Hortensia de plebiscitis.” Archiv für Kulturgeschichte 70, no. 2 (1988): 271–312.
  • Kubitschek, Wilhelm. Die Kalenderbücher von Florenz, Rom und Leyden. Denkschriften der kaiserlichen Akademie der Wissenschaften in Wien, phil.-hist. Kl. 57, 3. Vienna, Austria: Hölder, 1915.
  • Laffi, Umberto.“Le iscrizioni relative all'introduzione nel 9 a. C. del nuovo calendario della provincia d'Asia.” Studi Classici e Orientali 16 (1967): 5–98.
  • Olzscha, Karl.“Die Kalenderdaten der Agramer Mumienbinde.” Aegyptus 39, no. 3/4 (1959): 340–355.
  • Pfiffig, Ambros Josef. Studien zu den Agramer Mumienbinden (AM) (Der etruskische liber linteus). Österreichische Akademie der Wissenschaften, Phil.-hist. Kl. 81. Vienna, Austria: Böhlau, 1963.
  • Rüpke, Jörg. Kalender und Öffentlichkeit: Die Geschichte der Repräsentation und religiösen Qualifikation von Zeit in Rom. RGVV 40. Berlin, Germany: de Gruyter, 1995.
  • Rüpke, Jörg.“[Review] F. Cristofani, Tabula Capuana …” Gnomon 71, no. 3 (1999): 272–274.
  • Rüpke, Jörg.“Ennius' fasti in Fulvius' Temple: Greek Rationality and Roman Tradition.” Arethusa 39, no. 3 (2006): 489–512.
  • Rüpke, Jörg. The Roman Calendar from Numa to Constantine: Time, History and the Fasti. Translated by David M. B. Richardson. Malden, MA: Wiley-Blackwell, 2011
  • Rüpke, Jörg. 2012. Religion in Republican Rome: Rationalization and Ritual change. Philadelphia: University of Pennsylvania Press.
  • Salzman, Michele Renée. On Roman Time: The Codex-Calendar of 354 and the Rhythms of Urban Life in Late Antiquity. Berkeley: University of California Press, 1990.
  • Samuel, Alan E. Greek and Roman Chronology: Calendars and Years in Classical Antiquity. Munich, Germany: Beck, 1972.
  • Stern, Sacha. Calendars in Antiquity: Empires, States, and Societies. New York: Oxford University Press, 2012.
  • Woudhuizen, Fred. The Etruscan Liturgical Calendar from Capua. Amsterdam, The Netherlands: Gieben, 1996.