The website at goskateboardingday.org says that today "skateboarders around the globe celebrate the pure exhilaration, creativity, and spirit of one of the most influential activities in the world by blowing off all other obligations to go skateboarding."
I'm not entirely certain that skateboarding ranks up there with the "most influential activities in the world" but, if you enjoy skateboarding, be sure to carpe diem. One suggestion, however, if I might: Don't plan on skateboarding after you've celebrated Go Skateboarding Day at your favorite public house.
Not that Go Skateboarding Day isn't likely to be celebrated with increasing fervor in the decades and centuries to come, but it may be worth noting that June 21 is also the anniversary of the first privately-funded manned space flight.
On this day, eight years ago, SpaceShipOne flew, albeit briefly, into outer space. Says Wikipedia:
Flight 15P on June 21, 2004, was SpaceShipOne's first spaceflight, and the first privately funded human spaceflight. There were a few control issues, but these were resolved prior to the Ansari X PRIZE flights that followed, with flight 17P on October 4, 2004, winning the prize.Someday, that anniversary may be almost as important as Go Skateboarding Day.