According to Wikipedia: "International Surfing Day, held annually on or near the date of the summer solstice — usually June 21 (June 20 on leap years) — is an unofficial, environmentally conscious sports-centered holiday that celebrates the sport of surfing and the surfing lifestyle and the sustainability of ocean resources".
However, the summer solstice was on June 20 in 2013 although it is not a leap year. Therefore, the International Surfing Day in 2013 actually falls on June 20. Nonetheless, The events celebrating the International Surfing Day spreads from June 17 to June 23, and onto June 30, 2013. Chances are you can probably find a location near you (except in Las Vegas, where the closest ocean is more than 270 miles / 435 km away).
Fortunately, there is a huge man-made beach at the Mandalay Bay. I bought this postcard US-2255631 at Ron Jon Surf Shop in the Shoppes at Mandalay Place.