There are certain articles online describing this story as something similar to No Pants Day which happens every first Friday in May. Unlike that particular event, No Panty Day stays too informal and promotions of this international holiday to rid women's panties remains limited to social media.
The observance of No Panty Day has no clear origin nor the organizers of the group haven't surfaced online in the past five years. You might bump into a Facebook page whose topics are related to this celebration but as mentioned, no one has really proven the validity of this annual event.
So, what are you waiting for? Drop your underwear and celebrate no panty day 2016!