The Ancient Roman Calendar

The Roman calendar went through several different guises before settling down to the one we use today. I will put a history of the calendar here at some future date, but at the moment, I will give a short explanation as to how the calendar works.

The calendar used in on this site is the one that became known as the Julian calendar after Julius Caesar, who devised it in 46 B.C.E. We now use the Gregorian calendar, which was altered from the Julian in 1582 C.E. This alteration was, however, made to the frequency of leap years rather than to the actual structure, which is the same now as the one devised by Caesar. The difference in Roman times was the way the dates were expressed.

Each month had three main days, the Kalends, the Nones and the Ides. The Kalends were on the first of the month. The Nones were on the 5th of the month for all months except March, May, July and October, when they were on the 7th. The Ides were 8 days later than the Nones, i.e. on the 13th or 15th of the month. The intervening days were counted backwards, inclusively, to the next of these main days. So, for example, the 15th of March was the Ides of March, or Idibus Martius. The 14th March was Pridie Idibus Martias, or the "day before the ides of March". The 13th was the 3rd day before the Ides, or ante diem III Idibus Martius, showing the inclusive nature of Roman counting, i.e. three days before the 15th was the 13th inclusively (13 - 14 - 15).

This system was used for all the three main days of the month, and thus produced something that seems odd to us now. The dates following the Ides of each month refer to the Kalends of the following month, e.g. the 18th December was ante diem XV Kalendis Ianuarius, or "15 days before the Kalends of January". Note that the year number still did not change until the Kalends, however, i.e. the 1st January.

These dates were usually abbreviated, e.g.

Idibus Martius = ID. MART.
Pridie Idibus Martias = PRID. ID. MART.
ante diem III Idibus Martius = A.D. III ID. MART.
ante diem XV Kalendis Ianuarius = A.D. XV KAL. IAN.

These abbreviateions are used for the Roman date on the main calendar page.

The days of the week are shown in Latin, with the nundinal letter for the day shown alongside in brackets. This was a form of eight-day week, lettered 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. 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'. The market day letter for the current year is shown in brackets beside the year. When the current day is a market day, I have denoted this with an asterisk beside the nundinal letter for the day.

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 first of these days is labelled bis, i.e. A.D. (bis) VI KAL. MART.

The epoch for the year that has been used in 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").