(Antiquité) Division du mois.
In the Roman calendar: the 15th of March or May or July or October or the 13th of any other month.
pl. 13th or 15th day of month in ancient Roman calendar. ides of March, unlucky or fatal day.
In the Roman calendar, the 15th day of March, May, July, and Oct, and the 13th day of all other months (the word originally indicated the full moon); Julius Caesar was assassinated on the Ides of March 44 BC.