The Julian and Ancient Roman Calendars

The Julian calendar is named after Julius Caesar, during whose reign it was adopted by the Roman empire, and is, essentially, the calendar we use today, excepting the minor change instituted by Pope Gregory XIII in the Gregorian calendar reform of 1582. Prior to the institution of the Julian calendar, the Romans had a relatively complicated calendar that was originally lunar, with months of 29 and 31 days and a thirteenth, intercalary month every few years to keep it in line with the solar year. The image below shows a tablet detailing this calendar, with the figures at the bottom showing the number of days in each month.

Stone tablet detailing the original Roman calendar

This shows the months as Ianuarius (29 days), Februarius (29), Martis (31), Aprilis (29), Maius (31), Iunius (29), Quintilis (31), Sextilis (29), Sepembris (29), Octobris (31), Novembris (29) and Decembris (29). The last column is the intercalary month, with 27 days, that was added when required, as the normal year only had 356 days, nine short of a standard year.

As time went on, the calendar went into a state of disarray, as the intercalary month was often not added when it should have been, or added more than once, in order to satisfy superstitions or lengthen the years, which were named after the current leaders of Rome, to suit personal ambitions. Eventually, Julius Caesar reformed the calendar, basing it on the Egyptian solar calendar of 365 days, and introduced the leap year of 366 days every four years to keep it in synchronisation with the solar year. The months now had the same number of days as today, and it can be seen from this that the theory that Februrary had a day "stolen" from it to make August longer, thus leaving it with only 28 days, are in fact false.

After Caesar's death, the month of Quintilis was renamed Iulius (July) in his honour. Unfortunately, the authorities made an error with the application of the leap years, applying it every three years instead of four. To correct the error, Augustus Caesar dropped some subsequent leap years, and Sextilis was renamed Augustus in his honour.

In the Roman calendar, however, the system of counting days was very different. The months contained three primary markers - the Kalends, the Nones and the Ides. The Kalends were always the first day of the month. The Nones were on the 5th of the month and the Ides on the 13th, except in March, May, July and October, when they fell on the 7th and 15th respectively (note that these months were the ones that had 31 days in the original calendar). The days in between were numbered by counting down towards the next marker day. This was done inclusively, so the 11th January was the "third day before the Ides" and the 12th was the "day before" (Pridie), etc. All the days after the Ides were numbered by counting down towards the next month's Kalends, so the 15th February was actually called the 15th day before the Kalends of March. The following table shows how this worked, using the first three months of the year as an example.

January IANVARIVS February FEBRVARIVS
March
MARTIVS
1 KALENDS IAN. 1 KALENDS FEB.
1
KALENDS MAR.
2 IV NON. IAN. 2 IV NON. FEB.
2
VI NON. MAR.
3 III NON. IAN. 3 III NON. FEB.
3
V NON. MAR.
4 PRIDIE NON. IAN. 4 PRIDIE NON. FEB.
4
IV NON. MAR.
5 NONES IAN. 5 NONES FEB.
5
III NON. MAR.
6 VIII ID. IAN. 6 VIII ID. FEB.
6
PRID. NON. MAR.
7 VII ID. IAN. 7 VII ID. FEB.
7
NONES MAR.
8 VI ID. IAN. 8 VI ID. FEB.
8
VIII ID. MAR.
9 V ID. IAN. 9 V ID. FEB.
9
VII ID. MAR.
10 IV ID. IAN. 10 IV ID. FEB.
10
VI ID. MAR.
11 III ID. IAN. 11 III ID. FEB.
11
V ID. MAR.
12 PRIDIE ID. IAN. 12 PRIDIE ID. FEB.
12
IV ID. MAR.
13 IDES IAN. 13 IDES FEB.
13
III ID. MAR.
14 XIX KAL. FEB. 14 XVI KAL. MAR.
14
PRID. ID. MAR.
15 XVIII KAL. FEB. 15 XV KAL. MAR.
15
IDES MAR.
16 XVII KAL. FEB. 16 XIV KAL. MAR.
16
XVII KAL. APR.
17 XVI KAL. FEB. 17 XIII KAL. MAR.
17
XVI KAL. APR.
18 XV KAL. FEB. 18 XII KAL. MAR.
18
XV KAL. APR.
19 XIV KAL. FEB. 19 XI KAL. MAR.
19
XIV KAL. APR.
20 XIII KAL. FEB. 20 X KAL. MAR.
20
XIII KAL. APR.
21 XII KAL. FEB. 21 IX KAL. MAR.
21
XII KAL. APR.
22 XI KAL. FEB. 22 VIII KAL. MAR.
22
XI KAL. APR.
23 X KAL. FEB. 23 VII KAL. MAR.
23
X KAL. APR.
24 IX KAL. FEB. [24] [BIS. KAL. MAR.]
24
IX KAL. APR.
25 VIII KAL. FEB. 24 [25] VI KAL. MAR.
25
VIII KAL. APR.
26 VII KAL. FEB. 25 [26] V KAL. MAR.
26
VII KAL. APR.
27 VI KAL. FEB. 26 [27] IV KAL. MAR.
27
VI KAL. APR.
28 V KAL. FEB. 27 [28] III KAL. MAR.
28
V KAL. APR.
29 IV KAL. FEB. 28 [29] PRID. KAL. MAR.
29
IV KAL. APR.
30 III KAL. FEB.    
30
III KAL. APR.
31 PRIDIE KAL. FEB. [ ]=Leap Year
31
PRID. KAL. APR.

This system was used for centuries afterwards, and it was only around the 11th to the 13th centuries that our current system of numbering from 1 to 28, 29, 30 or 31 really came into widespread use.

Nundinal letters and market days

In the Roman calendar, the nundinal letter was like an equivalent of the modern days of the week, except with eight days instead of seven. Each day was lettered successively from A to H. Every eighth day (ninth day using the Roman inclusive counting system, hence the word nundinal) was a market day, which was a special day in Roman times, so wthhin a particular year the market days all had the same nundinal letter, and that letter was designated as the nunidanl letter for that year. Each date had the same nundinal letter from one year to the next, because the sequence was reset to 'A' at the beginning of the year. This meant that, applying the strict eight-day rule for market days, the letter for the market day changed from one year to the next. So, for instance, in 2007 the market day letter is 'H', which means that the last market day of the year would have been 26th December. The next market day would be 3rd January, so the market day letter for 2008 would be 'C'.

Leap years

In leap years, the 6th day before the Kalends of March (a.d. VI Kal. Mart.) was effectivley doubled, hence why a leap year is often called a bissextile year. Effectively, the 24th of February in a leap year is inserted, thus pushing the remaining days of that month back by one day. The 25th, then, has the same nundinal letter as the 24th, and the remaining dates have their correct nundinal letters. So, for instance, Prid. Mart. always has nunindal letter 'C', even though in our modern calendar it is 28th February in a normal year, and 29th February in a leap year. To the Romans they were the same date. In the calendar, the second of these days is labelled bis, i.e. a.d. (bis) VI Kal. Mart.

Epoch

The epoch for the year that has been used here is 753 B.C.E., which is the most favoured date for the foundation of the city of Rome, thus 2007 C.E. is the year 2760 A.U.C. (ab urbe condita - "since the foundation of the city").