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Ancient Calendars 8: Rome

“And so we came to Rome” (Acts 28:14). In this final installment we’ll survey the calendars of ancient Rome and environs.

Evidence exists for four calendars from ancient Italy. No account of the moon was taken in the Roman systems known to us.

Romulus (8th–7th cent.?) Etruscan Old Roman (7th–6th cent.?) Julian (45 BC)
Mar Martius Velcitna Martius Martius
Apr Aprilis Capre Aprilis Aprilis
May Maius Ampiles, Amphiles Maius Maius
Jun Iunius Acale Iunius Iunius
Jul Quintilis Masan,
Masn (?)
Quintilis Quintilis
Aug Sextilis Hermi Sextilis Sextilis
Sep September Celi September September
Oct October Chosfer October October
Nov November ? November November
Dec December ? December December
Jan n/a ? Ianuarius Ianuarius
Feb n/a ? Februarius Februarius

The (1) “year of Romulus” was a primitive agricultural year, divided into ten months of irregular lengths of up to 39 days.

This calendar was eventually replaced by the (2) Etruscan lunar calendar, which eventually gave rise to the old Roman calendar. The Etruscan calendar began with the “Ides of March,” first full moon after the vernal equinox. In addition to the months listed above, there was also has a month called Thucte whose position is unknown. Masan (“sacrifice”) is also disputed, but perhaps is comparable to the Canaanite ZBḪ ŠMŠ (“sacrifice of the sun”).

The (3) old Roman calendar consisted of 12 months; 4 of 31 days (Martius, Maius, Quintilis, October), 7 of 29 (Ianuarius, Aprilis, Iunius, Sextilis, September, November, December), and one of 28 (Februarius), totaling 355 days in a year. Every other year (even-numbered years BC) an intercalary month, Mercedonius (or Intercalaris), was added after 23 February and lasting 27 or 28 days (the total intercalation was thus 22 or 23 days—approximately one day longer than the tropical year). In later periods, the pontifices determined intercalation. Eventually (by c. 153 BC?) New Year’s Day was moved back to 1 Ianuarius. In Rome, market-days were spaced at eight-day intervals.

Days of the month were not numbered but rather counted relative to three key dates that occurred each month. The Kalends (kalendae) of the month was the first day; the Nones (nonae) was the 7th day of a 31-day month or the 5th day of a 29-day month. The Ides (idus) was the 15th day of a 31-day month or the 13th day of a 29-day month. Originally, these days marked the new moon, first quarter, and full moon. Days were counted down to the next benchmark. Thus, for example, the 13th of Martius was “the third day before the Ides of Martius” and the 4th of Quintilis was “the fourth day before the Nones of Quintilis.”

Julius Caesar abandoned the old Roman calendar and instituted in its place the (4) Julian calendar, a solar calendar of 365.25 days, which was stable and agreed with the seasons. Every fourth year a leap day was inserted after 24 Februarius. In the earliest decades, a leap year was erroneously added every third year instead of every fourth. The discrepancy was eventually corrected in AD 8.

In early imperial times years were sometimes counted from Octavian’s victory at the Battle of Actium (2 September, 31 BC).

According to tradition, the city of Rome was founded in 753 BC. Some Roman historians counted years ab urbe condita (“from the founding of the city”), although this does not seem to have been a widespread dating method. Modern historians use the AUC epoch much more frequently than the Romans did.


  • E. J. Bickerman, Chronology of the Ancient World, 2nd ed. (Cornell University Press, 1968).
  • ________, “calendar.” Encyclopædia Britannica. 2010. Encyclopædia Britannica Online.
  • Giuliano and Larissa Bonfante, The Etruscan Language (Manchester University Press, 2002).
  • Holger Oertel, “Several Calendars.”
  • Alan E. Samuel, Greek and Roman Chronology (Taylor and Francis, 1972).


  1. Bill says:

    Great post, Darrell. But I have one minor yet troubling question.

    Was or was not the eclipse of 4 BC on the Roman date “March 13th”? (I mean, after 41 years, with about 13 leap days instead of the more proper ten, the Roman calendar may have said March 16th, where we’ve estimated it said 13th.) Is it off? Or did the experts take this into account long, long ago? Do you know?

    At any rate, I’m not sure I recall hearing about this before, so I’d be most grateful for a specific citation on the fix of 8 AD… when you next get a minute, please kind sir. 🙂


  2. Darrell Pursiful says:

    Thanks, Bill. I found the AD 8 fix noted in Bickerman, Chronology of the Ancient World. The book is in my office and I’m iced in at home at the moment, so I can’t provide a page number. I’m afraid I know nothing about where to find the 4 BC eclipse on the Roman calendar. I assume you’re hunting for evidence for or against this being the eclipse that occurred before Herod’s death?


  3. Bill says:

    Sorry replying so late, and for being unclear. I’m pretty sure a day or two difference doesn’t affect our conclusions about Herod’s death. So I’m not troubled about that, but simply in wondering whether myriads of scholarly literature has overlooked a minor inaccuracy.

    When that eclipse did occur, reportedly at about 3 AM local time, did the Julian Calendar say “March 13” or “March 12” or “March 14”? I just want to know, accurately.

    It seems we have another reason to be wary of March’s Ides. 😉


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