According to Wikipedia, this Saturday marks the shared birthday of Kareem Abdul-Jabbar, Bill Belichick, Peter Billingsley, Jon Cryer, and Martin Lawrence. Only now it will also, according to New York City Mayor Michael Bloomberg, be Foursquare Day.
Bloomberg issued an official proclamation on the subject today. It (in part) read, "New York City is proud to be the home of both the powerhouse companies and small startups that are thinking big, creating new jobs, and leading the global economy. Foursquare is one such success story. Started by Dennis Crowley and Naveen Selvadurai around Dennis's kitchen table in the East Village, it now employs more than 60 people in New York and has more than eight million users worldwide."
Then the proclamation continued, "That is why we are proud to join Foursquare's founders and fans in celebrating the first global social media holiday. Today, April 16th - 4/16, the fourth sixteenth of the year - is Foursquare Day in New York City and around the world."
This development represents quite an honor for the company. It's a solid piece of PR/advertising, too, and seems sure to cause at least a small uptick in Foursquare users.
The one small downside (which can't be helped) is that 4/16 is indeed a Saturday this year, meaning a lot of journalists and bloggers who would otherwise generate publicity will take the day off. A lot of potential users will be mowing their lawns and lounging around the house, for that matter, rather than learning about Foursquare and checking into various places.
Anyway, happy Foursquare Day in advance.