The middle of May; approximately May 15th. This is the general date at which all high-school seniors have gotten where they want to be and thus, stop caring about high school. This coincides with the point in the grading term in which they can still pass their classes without doing any work from there on out.
This is a play on words, referring to the Ides of March
. Much like Caesar's downfall, the Ides of May lead to the downfall of many seniors because they often fail to do the gradebook math correctly (their brains are fried, give 'em a break).
"Beware the ides of May... for along with the flowers, senioritis
shall be in full bloom."
A: "The Ides of May are approaching, dude..."
B: "Fuck, my college requires a final transcript. Shit."
A: "Lame. Wanna hit up a party later on anyway?"
A: "You too, Brutus?"