We've ranted before about the misuse of the term 'ides' to refer to the fifteenth of any month, despite the old mnemonic (one version):

In March, July, October, May
The ides fall on the 15th day,
The nones are on the 7th

... the rest have the Ides on the 13th, of course. So all the authors/editors of those articles today which are referring to 'tax day' in the US as the "ides" really deserve a whack with the rc thyrsus of correction ...