It's "International Talk Like A Pirate Day!"
According to Wikipedia: International Talk Like a Pirate Day (ITLAPD) is a parodic holiday created in 1995 by John Baur (Ol' Chumbucket) and Mark Summers (Cap'n Slappy), of Albany, Oregon. who proclaimed September 19 each year as the day when everyone in the world should talk like a pirate. For example, an observer of this holiday would greet friends not with "Hello," but with "Ahoy, matey!" The holiday, and its observance, springs from a romanticized view of the Golden Age of Piracy.
So...when you head out to lunch or dinner...shock your server when you say: "Surrender The Booty!" (Be aware that this may cause some men to be slapped! LOL!)