ides / īdz/ • pl. n. (in the ancient Roman calendar) a day falling roughly in the middle of each month (the 15th day of March, May, July, and October, and the 13th of other months), from which other dates were calculated. Compare with nones, calends.

ides in the ancient Roman calendar, a day falling roughly in the middle of each month (the 15th day of March, May, July, and October, and the 13th of other months) from which other dates were calculated.
beware the Ides of March according to Plutarch, a warning given by a soothsayer to Julius Caesar that he would be in great danger on the Ides of March; Caesar was assassinated on that day.

ides Day in the Roman Republican calendar. They fell on the eighth day after the nones of each month, that is on the 15th of March, May, July and October and on the 13th of the other months. Julius Caesar was assassinated on the Ides of March.

Ides in the ancient Roman Calendar, the 8th day after the Nones. XV. — (O)F. — L. īdūs (pl.), perh. of Etruscan orig.