Harry Potter and the Half-Blood Prince, the sixth instalment in the blockbuster film franchise about boy wizard Harry, is moving from its planned 21 November US release to 17 July next year, distributor Warner Bros said.
The move was made to take advantage of an open weekend in Hollywood's busy summer season, said Alan Horn, Warner Bros president and chief operating officer.
The film had been on schedule, and the change was not due to any production snags, he said.
"The picture is completely, absolutely, 100 per cent on schedule, on time. There were no delays," Mr Horn said. "I've seen the movie. It is fabulous. We would have been perfectly able to have it out in November."
The switch will mean a two-year lag between the film adaptations of books five and six in JK Rowling's fantasy series.
But it will shorten fans' wait between Half-Blood Prince and the final two installments, which are being shot simultaneously next year.
Based on book seven, Harry Potter and the Deathly Hallows, the last two movies are due out in close order, in November 2010 and summer 2011.
Mr Horn said the later release of Half-Blood Prince will not affect the schedule for the final two movies.