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  • Leap Year – February 29

    Zach Beasley

    Leap Year – February 29

    One of the most well-known events of ancient Rome occurred on March 15, 44 BC – the assassination of Julius Caesar. But, what is the “Ides of March” of which Caesar was warned by a seer to beware? The Roman calendar didn’t mark dates numerically as we do today. Instead, they had three fixed points in each month and worked their way backwards from those three points. The three points were the Nones, Ides and Kalends.


    The original Roman calendar, the Calendar of Romulus, was said to have been made by the founder of Rome in 753 BC. This calendar consisted of 10 months of either 30 or 31 days, equaling 304 days, with the remainder of days in winter unassigned to any month and called the “intercalary month”. The ten months and their origins were Martius (Mars the god), Aprilis (Virilis the goddess), Maius (Maia the goddess), Iunius (Juno the goddess), Quintilis (Quinque or Five), Sextilis (Sex or Six), September (Septem or Seven), October (Octo or Eight), November (Novem or Nine) and December (Decem or Ten).

    Around 713 BC, Numa Pompilius, the second of the seven traditional kings of Rome, reformed the calendar. Since the Romans considered odd numbers to be lucky, Pompilius removed a day from each of the months with 30 days, combined them with the days in the intercalary month, and created two new months at the beginning of the calendar – Ianuarius (29 days) and Februarius (28 days). This new calendar had 355 days falling in four months of 31 days (Martius, Maius, Quintilis and October), seven months of 29 days and Februarius with 28 days. Februarius was given an unlucky number of days, but was accepted because it was a month of purification. Also, although Februarius had 28 days, it was actually broken into two parts – the first was 23 days long and finished with the Terminalia and the final five days were another part. Still, that left 10 to 11 unaccounted for days in the year, so those ended up as a “leap month”, called the Mensis Intercalaris, which was added between the two parts in Februarius about every other year to keep the calendar roughly aligned with the solar year.

    Since the Romans did not sequentially date each day in each month, they needed to spell out how they were counting backward from the next monthly point. The Kalends (or Kalendae) was the first day of the month, the Nones (or Nonae) was the 5th or 7th of the month, depending if the month had 29 or 31 days, and the Ides (or Idus or Eidus) was the 13th or 15th. Februarius followed the short months for the Nones and Ides. The Romans preceded their dating with a.d. for ante diem and the day of the fixed point counted as the first day of the backwards counting. Thus, they would date a document, etc. as:

    a.d. III Non. Apr. = Three days before the Nones of Aprilis (29 days) = Aprilis 3

    a.d. III Non. Mai. = Three days before the Nones of Maius (31 days) = Maius 5

    a.d. V Id. Sep. = Five days before the Ides of September (29 days) = September 9

    a.d. V Id. Qui. = Five days before the Ides of Quintilis (31 days) = Quintilis 11

    a.d. VIII Kal. Ian. = Eight days before the Kalends of Ianuarius = December 23 (29 days)

    a.d. VIII Kal. Mart. = Eight days before the Kalends of Martius = Februarius 22 (28 days)

    a.d. VIII Kal. Iun. = Eight days before the Kalends of Iunius = Maius 25 (31 days)

    The exception to the spelling out of the dates is the day before the three monthly points. That day was called the Pridie and would be denoted as Prid. Non. Sex. = The day before the Nones of Sextilis, or Sextilis 4. The three points themselves are straightforward abbreviations. March 15 would simply be Id. Mart. or Eid. Mar.

    The office of the Pontifex Maximus was in charge of determining when the intercalary month was needed and the result was intercalary years being 377 or 378 days long, depending if Intercalaris began one or two days after Terminalia. Since the offices of the Roman magistrates were elected each year, the Pontifex Maximus being one of them, that office could lengthen their time in power by controlling the length of the year. Julius Caesar, while holding the office of Pontifex Maximus in his third consulship in 46 BC, made that Roman year 445 days long.

    Julius Caesar also reformed the calendar in 46 BC, which was then known as the Julian Calendar, and took effect in 45 BC. It cleaned up the issue of the intercalary month by making a fixed 365.25 day year and added a leap day to Februarius every fourth year, 2016 being one of the years where the extra day is needed. In 44 BC, the month of Quintilis was renamed Iulius in honor of Julius Caesar and the reforms were completed under Augustus in 8 BC, when the Senate renamed Sextilis to Augustus in honor of the new emperor. The Julian calendar remained in place as designed, and used in the Roman world, most of Europe, European settlements and the Americas and elsewhere until Pope Gregory XIII made a 0.002% change to it in 1582 to deal with the accumulated differences in the extra 10 minutes and 48 seconds per day since the Julian calendar was introduced. This became the Gregorian calendar we use today, but the correction still needed to be implemented to adjust for the time over the centuries, which had grown to 10 days. The final date of the Julian calendar is Thursday, October 4, 1582 and the first day of the Gregorian calendar is Friday, October 15, 1582. The ten-day period in between was simply deleted. Some countries adopted the new calendar immediately, but some, like the British Empire, didn’t until 1753.

    Julius Caesar, on the way to the Theater of Pompey, passed by the seer that warned him harm would come to him by the Ides of March and said mockingly “The Ides of March have come”, to which the seer replied “Aye, Caesar; but not gone”.  Before the end of the day, Caesar was assassinated on the Senate floor by as many as 60 conspirators, led by Brutus and Cassius, and commemorated on one of the most famous issues of Roman coinage – the Eid Mar, showing two daggers and a pileus.


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