We have just received confirmed word from Warner Bros that the Japanese premiere of Half-Blood Prince will take place on Monday, July 6, 2009. The date was first announced at a fan event that took place in Japan on April 19, after which we inquired on the date.
Warner Bros also states that this is the FIRST world premiere, and that two more will take place afterwards in London and New York. The London premiere will take place on Tuesday, July 7th, and the New York City premiere the next day, on July 8th.
At the moment we do not know which of the stars will be attending the Japanese premiere; that information will be made public closer to the July date.