In a post on the studio's community website, Gearbox president Randy Pitchford says that the delay has come from the studio's insistence that quality will not be compromised by deadlines, adding that, by the time it comes out, Colonial Marines will have been in development for roughly the same amount of time as Borderlands and the original Brothers in Arms.
"We're now at a point in development where we can see the end," he writes. "We know what's left to do and can sufficiently quantify it to be very confident in the schedule for the game's completion and commercial release.
"We're very excited to finally have a firm date, and can't wait for you to step into the boots of a colonial marine and kick some ass."
Colonial Marines, Gearbox's semi-sequel to James Cameron's 1986 film Aliens, was officially announced in February 2008, though Gearbox and publisher Sega first revealed that a new Aliens game was in the works in December 2006. It starred on the cover of Edge 240, and you can read a recent preview of the game here.
It has already been delayed once this year, with its original spring launch window pushed back to autumn. This is the first time the game has had a specific launch date, and to mark the occasion, Gearbox has released the below new trailer.