Explanation for Half-Blood Prince move to July 15th

The Associated Press has a new article online with a quote from Warner Brothers Head of Distribution Dan Fellman. He explains why they moved the date of Harry Potter and the Half-Blood Prince from July 17th to July 15th:

That gives the movie a head-start on the weekend during what's shaping up as a highly competitive summer season for Hollywood, which has major franchise films opening virtually every week.

“Every day the kids are out of school in summer is just like an extra Saturday,” Fellman said.