HBO has added a Game of Thrones special, titled Game of Thrones: A Day in the Life, to their programming schedule, to air on February 8 at 7:30 p.m. ET. The addition was first spotted by a reader who tipped off Game of Thrones fansite Winteriscoming.net.
Last year, at nearly the exact same point in the year, HBO aired Ice and Fire: A Foreshadowing, a kind of preview featurette for Game of Thrones Season 4. We don't know for sure, but A Day in the Life seems likely to be the same kind of feature, but for the show's upcoming fifth season. The pevious special featured a behind-the-scenes look at the making of the season, interviews with the cast, and new footage from the upcoming season.
If HBO airing another special at the same point on their schedule as last year is an indication that they are following the same release pattern as they did with Season Four, then it seems likely that we'll begin seeing promotional art for the new series soon, and will likely see the first full trailer in mid-January (viral marketing for Season 5 has already begun). This will likely lead to an early April premiere.