(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 (古罗马历法用语)月中日(3、5、7、10月的15日,其余月份的13日)。 比较 nones, calends
语源
late Old English: from Old French, from Latin idus (plural), of unknown origin