Warner Bros. gave Harry Potter the school year off, announcing last week it was bumping the sixth movie in the series to next summer from this fall. But Entertainment Weekly — which shares the studio’s parent company, Time Warner Inc. — was unaware of the change, featuring “Potter” star Daniel Radcliffe on the cover of its August 22-29 fall-preview issue.

The magazine leads off the issue with a six-page spread pegged to “Harry Potter and the Half-Blood Prince,” which Warner Bros. on Thursday moved to July 17, 2009, from its previous November 21 release date.

The studio had been considering the date change for three or four weeks, “but it really didn’t kind of get on the front burner until sometime within the last seven days,” the Warner Bros. head of distribution, Dan Fellman, said Sunday.

Entertainment Weekly’s “deadline must have been earlier than the decision, than when we started to get serious about making the decision,” Mr. Fellman said.

The magazine’s online edition added a preface about the date change to the “Harry Potter” story. It also had a laugh or two about the lack of communication between two Time Warner outfits.

“In an irony sure to set blogger hearts beating giddily, the film graces the cover of EW’s new fall preview issue,” reads an entry on the magazine’s Hollywood Insider Web log. “EW and Warner Bros. share a parent company, but they clearly do not share, you know, important … information.”

The blog goes on to joke that the date change will leave Entertainment Weekly “readers in possession of a ‘Dewey Beats Truman’ collectible.” It also notes that the British film magazine Empire features Harry Potter on its current cover, though that issue touches on big 2009 releases, as well.

Warner executives said the date change was a business decision and not due to any production delays on “Half-Blood Prince.” A recent Writers Guild of America strike had delayed production on some films, leaving a lighter lineup during 2009’s busy summer season, Mr. Fellman said.

The July 17 release — the same weekend Warner Bros. debuted its blockbuster “The Dark Knight” this summer — offered better box-office potential for “Half-Blood Prince,” Mr. Fellman said.

The change left a hole in Hollywood’s overall schedule for November 21, the week before Thanksgiving, one of the busiest weekends for theaters.

But fantasy fans will not have to do without: A day after “Half-Blood Prince” moved out, Summit Entertainment’s vampire romance “Twilight,” based on another best-selling series of books, moved in, switched to November 21 from its scheduled December 12 release.