Emily Dickinson Lexicon

IDES, n. [plur. L. idus. Qu. the Hetrurian iduo, to divide, the root of wide, divide, individual. The etymology is not ascertained.]

In the ancient Roman calendar, eight days in each month; the first day of which fell on the 13th of January, February, April, June, August, September, November and December, and on the 15^th of March, May, July and October. The ides came between the calends and the nones, and were reckoned backward. This method of reckoning is still retained in the chancery of Rome, and in the calendar of the breviary. Encyc.