It has been confirmed by the Radio Times that the start date for The Impossible Astronaut will be 6pm Saturday 23rd April. This is one of the earliest times the programme has started in recent years.
Doctor Who Confidential will be at 7pm as BBC3 starts broadcasting. This weeks Radio Times (16-22) contains an interview with Steven Moffat, you can read it here. Also featured in the Radio Times is Steven's preview to the first seven stories of series 6 and an interview with Matt Smith