Allen and Greenough's New Latin Grammar for Schools and Colleges
J. B. Greenough, G. L. Kittredge, A. A. Howard, Benj. L. D'Ooge, Ed.

[*] a. The first day of the month was called Kalendae (Calends).

[*] Note.-- Kalendae is derived from calāre, to call,—the Calends being the day on which the pontiffs publicly announced the New Moon in the Comitia Calāta. This they did, originally, from actual observation.

[*] b. On the fifteenth day of March, May, July, and October, but the thirteenth of the other months, were the Īdūs (Ides), the day of Full Moon.

[*] c. On the seventh day of March, May, July, and October, but the fifth of the other months, were the Nōnae (Nones or ninths).

[*] d. From the three points thus determined, the days of the month were reckoned backwards as so many days before the Nones, the Ides, or the Calends. The point of departure was, by Roman custom, counted in the reckoning, the second day being three days before, etc. This gives the following rule for determining the date:—

If the given date be Calends, add two to the number of days in the month preceding,—if Nones or Ides, add one to that of the day on which they fall,—and from the number thus ascertained subtract the given date. Thus,—

1. VIII. Kal. Feb. (31 + 2 - 8) = Jan. 25.
2. IV. Nōn. Mār. (7 + 1 - 4) = Mar. 4.
3. IV. Īd. Sept. (13 + 1 - 4) = Sept. 10.

[*] Note.--The name of the month appears as an adjective in agreement with Kalendae , Nōnae , Īdūs .

For peculiar constructions in dates, see § 424. g.

[*] e. The days of the Roman month by the Julian Calendar, as thus ascertained, are given in the following table:—

[*] Note.--Observe that a date before the Julian Reform (B.C. 46) is to be found not by the above table, but by taking the earlier reckoning of the number of days in the month.