Roman Dates

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Conversion table: (Excel) (HTML) (CSV)                                                   Fasti consulares: (Excel) (HTML)

This page provides a brief overview of the major sources used to prepare the conversion table.


The most important single source for Roman calendrics is Macrobius, Saturnalia. Several chapters of this work discuss the evolution of the republican and Julian calendar in great detail. Macrobius wrote in the fifth century AD, but he drew on a large number of earlier sources, mostly now lost, most of which he names. Many of these were directly contemporary with the usage he describes, and were written by people who, by virtue of their position and expertise, were speaking with great authority. Not all of Macrobius' statements are reliable. His description of the management of intercalation in the republican calendar is confused, and his description of the mismanagement of the Julian reform does not appear to be completely correct. However, Macrobius remains central to any study of the Roman calendar.

Several authors provide additional information, most notably Censorinus. Additionally, surviving contemporary calendars -- fasti -- provide much additional detail. The most important of these are the Fasti Maffeiani and the Fasti Antiates Maiores. The Fasti Maffeiani, when first discovered in the 16th century, was an almost complete Julian calendar from the Augustan epoch. Although many fragments have been lost, it can still be studied through reproductions made in the 16th century. The Fasti Antiates Maiores, discovered in the 1920s, are the only pre-Julian fasti yet known, dating from the 60s B.C. Although they are quite fragmentary, enough survives that the structure of the original fasti can be recovered, allowing us to supplement and correct Macrobius.

The primary modern study used here is A. K. Michels, The Calendar of the Roman Republic (Princeton, 1967). I strongly recommend this book to anyone interested in calendrics. It is well-researched, highly knowledgeable, full of useful detail, well written, and sane. Additional papers on particular topics have been addressed as appropriate in the analysis section.


Calendrical data is not sufficient to recover Julian equivalents of Roman dates before the Augustan reform of 8 B.C. took full effect. This is because the occurrence and lengths of intercalation were not finally fixed until that time. In order to recover them for the purposes of constructing conversion tables, it is necessary to study Roman chronology in some depth.

The fasti consulares allows a rough equivalence of Julian year and Roman years to be established; the source issues for these are discussed here. In order to establish an exact Julian date, however, it is necessary to establish more exact synchronisms between Roman and Julian dates. This problem has been studied in depth at intervals since the 16th century, most intensively in the late 19th century. The main guide for these pages, considered here -- surely not quite accurately as the "standard" view -- is P. Brind'Amour, Le calendrier romain: recherches chronologiques (Ottawa, 1983). Additional studies of individual periods have also been used, though I have focussed on 20th century studies rather than the 19th century ones. In several periods, however, I have drawn my own conclusions which I believe go some distance beyond previous studies.

The sources are different for different periods.

The error bounds on seasonal synchronisms baselined on the eclipse of 190 B.C. exceed the size of an intercalation around the start of the First Punic War. It is not possible to use this technique to estimate intercalations before this date. Before 300 B.C. even the accuracy of the consular fasti becomes questionable, making it difficult to determine the Julian year of an event. In the absence of other astronomical, synchronistic or calendrical crosschecks -- the only possibility curently available is the eclipse of Ennius -- it is pointless to try to estimate exact conversions any earlier.

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