I ROMAN DATES

Until Julius Caesar reformed the calendar the Roman year consisted of 355 days divided into twelve months, all of which bore the Latin forms of their present names except Quintilis (= July) and Sextilis (= August). Each month had 29 days, except February with 28 and March, May, July, and October with 31. The first, fifth and thirteenth days of each month were called the Kalends (Kalendae), Nones (Nonae), and Ides (Idus) respectively, except that in March, May, July, and October the Nones fell on the seventh and the Ides on the fifteenth. Dates in classical Latin are expressed by the number of days before the next forthcoming Nones or Ides or Kalends, which-ever is nearest, prefaced by a. d. = ante diem. Thus a. d. IIII Non. Ian. (ante diem quartum Nonas Ianuarias) is the fourth day before the Nones of January, i.e., by inclusive reckoning, 2 January. The accusative after ante seems to have arisen through misunderstanding; die tertio ante Nonas would be logical. A date immediately before one of the three pivotal days is usually expressed by prid. (= pridie), though a. d. II also occurs.

To convert into modern dates: (a) If the point of reference is the Nones or Ides, subtract the number in the Roman date from the modern date of these Nones or Ides and add 1, as in the example above.