NASA needs to launch the next shuttle mission on time, because if it doesn't get off the ground by Dec. 18, a computer bug could mean the 12-day mission has to slip until January. "The Shuttle was never expected to be in orbit as one year gives way to another, so the computers aren't set up to switch to a new 'Day One.' To the Shuttle, January 1 is just day 366." That would leave the shuttle out of synch with NASA's ground-based computers.