nonae

Nonae is the Latin term used in the ancient Roman calendar to designate a fixed day within each month, situated between the Kalends (the first day of the month) and the Ides. The word derives from the Latin nona, meaning ninth, and it functioned as one of the three principal day-markers used to date events: Kalends, Nonae, and Idūs (Ides).

In the standardized Roman calendar, the Nonae fell on the seventh day in months that have 31 days (March, May, July, October) and on the fifth day in the other months (January, February, April, June, August, September, November, December). The Idēs then followed on the fifteenth day for the 31‑day months and on the thirteenth day for the shorter months. Days between these markers were counted inclusively, and dates could be expressed using the Latin phrase ante diem, followed by a number and either Nonas or Idus, to indicate how many days before the next marker a date occurred. For example, ante diem V Nonas means five days before the Nonae.

The Nonae held ceremonial and civic significance as fixed points in the calendar around which festivals and rites were organized. They also served as a conventional dating reference in Latin prose and inscriptions, especially in historical and legal texts.

With the Julian calendar reform, the civil calendar was reorganized, but the terms Kalends, Nonae, and Idus continued to appear in Latin literature as traditional markers. Today, nonaе are primarily of historical and linguistic interest, encountered in studies of the Roman calendar and ancient calendars more broadly.