It seems as though people aren't satisfied with celebrating the classic holidays anymore, so have resorted to straight-up creating their own. Which is probably how the world became blessed with quirky holidays such as: "Steak and Blowjob Day" and "No Bra Day". Just to be clear, we didn't invent these whacky events, but we do like to point out their existence, because quite frankly, they're pretty out-of-the-ordinary!
In this particular case, the holiday happens to be "No Panty Day" which takes place on Monday, June 22. There doesn't seem to be any underlying philosophy, or done to promote any special cause. From what we can tell, No Panty Day is literally only meant to give people an excuse to shamelessly go commando. Plus, as a wise man once said: "Ain't no party like a no panty party."
Of course, for some Montrealers who never wear panties to begin with, this might just be a day like any other. You could check out their Facebook page, but you won't find much info there other than the statement: It's simple - on 22nd of June - don't wear any panties.