ides is

It just occurred to me that I should have written that the ‘ides of March is upon us’, instead of what I wrote yesterday, which is “the ides of March are upon us”. I apologize for my poor grammar. The syntax of the sentence in question is still correct because the plural of ides is ‘ides’. However, I got it wrong since I intended to write about only one ides in particular. It is highly likely that I will commit many more offences of this nature over the course of my future writings. So consider yourself warned!