Nintendo is going to test the fields for Splatoon to give players a taste of the game before it launches on May 29th. Starting tomorrow, players will be able to try out Splatoon online during specific dates and times. Those event times are as followed: May 8th from 8:00PM to 9:00PM PST, May 9th from 4:00AM to 5:00AM PST, and May 9th from 12:00 Noon to 1:00PM PST.
This is a global event, hence why one of the times is during the morning hours. The Splatoon Global Testfire demo is available to download now, and booting it up during the times above will allow players to take part in the event. Hopefully this helps get the game into as many hands as possible, as the game is a lot of fun.