Happy 4sqDay indeed! Foursquare hits 20 million users and 2 billion check-ins

Just in case you’ve somehow missed it, today is 4sqDay! I hope everyone has fun celebrating my favorite wacky holiday.

Don’t forget to check in at some point today to unlock your 4sqDay badge. This year’s badge is my favorite design yet.

The unlock text reads:

In 2010, foursquare fans declared April 16 4sqDay (4/4^2 – nerds after our own heart!). Two years and two billion check-ins later, you’re still why we get out of bed each day. Thanks to all 20 million of you for making us part of your lives. Happy 4sqDay!

You’ll notice they snuck a sly little announcement in there. They’ve hinted at it for a few weeks, but it’s the first time foursquare has publicly said they now have 20 million users and two billion check-ins.

So, how did April 16 become 4sqDay? Back in 2010, Tampa optometrist Nate Bonilla-Warford realized that 4² = 16 and that April 16 would be a perfect day to celebrate foursquare. He got together with some friends and started putting together a worldwide movement. Other cities quickly joined in and parties were held all over the world that first year. It’s grown since then to include hundreds of cities in every corner of the globe.

Once again, the foursquare staff has put together a great video to say thanks for checking in and “Happy Foursquare Day!” to users worldwide: