Yanking 'Harry' stirs the plot pot

'Potter' is rescheduled, and studios scramble

"Harry Potter" fans are seething. "Twilight" devotees are in a state of giddy rapture. Will Ferrell's getting nervous. And someone had better perform CPR on the editors of Entertainment Weekly.

All because Warner Bros. decided last week that they needed one more blockbuster for the summer of 2009. The studio's announcement that "Harry Potter and the Half-Blood Prince" would be pushed back from its long-planned Nov. 21 release date this year to July 17 of next year was the pebble - more like the large rock - that started an avalanche of second-guessing and opportunistic rescheduling.

Driven by greed, hype, and hope, the business of exactly when to release a movie can seem inscrutable to outsiders. The sixth big-screen entry in the hugely successful "Potter" franchise had had the Thanksgiving weekend to itself; no studio was foolish enough to release a competing film against such a behemoth. With "Prince" decamped to 2009, though, a sudden void existed. Hollywood abhors a vacuum: Immediately Disney moved its 3-D family cartoon "Bolt" up from Nov. 26 to Nov. 21. Then the baby studio Summit Entertainment decided to move "Twilight" - the first film based on Stephenie Meyer's bestselling vampire romance novels and a movie awaited by millions of mostly young, mostly female, mostly panting readers - to Nov. 21.

That lets the one-time competition for "Twilight," 20th Century Fox's big-budget remake of the 1951 classic "The Day the Earth Stood Still," starring Keanu Reeves, have the weekend of Dec. 12 all to itself. Good news for Reeves, bad news for Ferrell, whose 2009 summer blockbuster "Land of the Lost" - another remake - is now in a July 17 stare-down with "Harry Potter." Someone has to blink, and it will probably be Universal, which doubtless has "Land of the Lost" theme-park blueprints already drawn up.

Why this insane chess game? Why does Hollywood care? In a word: Profits. Two words, really: Maximized profits. The decision to move "Half-Blood Prince" came because Warners looked ahead to the future and saw the ravages of the past. Specifically, the 2007 writer's strike had left the studio's summer 2009 slate lacking what the business calls a "tentpole" - a big event picture that can drive the planning, spending, and strategic release patterns of the company's entire output.

The dearth must have been critical - despite Warner's plans to release "Terminator Salvation" in May '09 - because no studio moves a tentpole at the last minute without a reason. Too many of the ancillary deals that make up the real business of the modern entertainment industry depend on a release date established early and adhered to. "The Dark Knight" was a July 18, 2008, release as of May 2007, because four scenes shot in the IMAX process meant the film had a hard date in IMAX theaters. And because "Knight" was anchored in place, other studios could plan around it, as could the various licensors who cling to a movie like remoras: videogame companies, toy manufacturers, fast-food chains, etc.

Who knows? Maybe Warners felt it had made enough money with "The Dark Knight" for 2008 and decided to spread the wealth to '09. (All right, I'm kidding.) More likely, the studio had one strong year and didn't want the following year to pale in comparison. The uprooting of "Half-Blood Prince" was sudden and unexpected, and, among others, it left the studio's corporate cousin, Entertainment Weekly, with a "Harry Potter"-themed Fall Preview issue on newsstands and serious egg on its face. (The decision to move "Prince" was announced on a Thursday; the magazine goes to the printer on Tuesdays.)

The release-date game has as much to do with maximizing hype as profits. Summit was delighted to bump "Twilight" up a month, because reader mania and media coverage reached near-"Potter" levels when the final book in the series, "Breaking Dawn," hit stores this summer. The closer the film is released to the fumes of all that free publicity, the better it may perform.

The strange case of the Tom Cruise drama "Valkyrie" offers an example of how an unreleased movie can rise and fall on the whims of buzz. A World War II movie about Colonel Claus von Stauffenberg (played by Cruise), a Nazi officer who led an unsuccessful plot to assassinate Adolf Hitler, the Bryan Singer film was originally scheduled to open Aug. 8, after a troubled location shoot in Germany. Then it bounced to June 28, where it was up against strong (if diverse) competition in "WALL-E" and "Wanted."

The chance to film an extra battle scene and a sense that "Valkyrie" might have Oscar potential resulted in a shift to Oct. 3, in the heart of awards season. Then the film got moved to Feb. 13, 2009 - not a good sign, since February and August have long been viewed as a dumping ground for films that just didn't work.

And then, the same day "Tropic Thunder" was released to rave reviews for Cruise's stealth role as a Hollywood producer, "Valkyrie" was moved again - to Dec. 26 of this year. The word is that a test screening went well, but it's hard to dismiss the notion that the star is back in moviegoers' good graces for the first time in years and that the studio hopes to piggyback on the warm fuzzies.

Occasionally two studios will engage in a stare-down with similar movies on the same date. This is almost always a bad idea for the worse of the two. Case in point: Warner's "Get Smart" with Steve Carell and Paramount's "The Love Guru" with Mike Myers were both scheduled early on for a June 20 release this summer. Neither budged, and when reviews savaged the Myers comedy, "Get Smart" benefited - a case of box office schadenfreude. On the other hand, Universal's decision to launch "Mamma Mia!" directly into the teeth of the "Dark Knight" juggernaut on July 18 proved to be a brilliant stroke of counterprogramming that gave older female audiences something to watch while the rest of the family lined up for Batman.

Does the movie-release shell game even matter to those whom it affects most directly - the moviegoers who pay for tickets and create the grosses? Is it important whether we get to see "Valkyrie" in October or December or next February? Not really, other than to set the parameters of the season's pop-culture conversation. Planned or accidental, this summer's blockbuster movie arc from one superhero to the next, culminating in the pop explosion of "The Dark Knight," determined many of the topics discussed in the public square. (Then there was the journey from Robert Downey Jr. as "Iron Man" to Robert Downey Jr. as a black man. Discuss.)

This much is certain: With the unparalleled glut of movies being released - 512 in 2007, up 45 percent from a decade before - someone has to figure out where the big ones go so the smaller films can find their place as well. When "Hancock" reigned supreme this past July 4th weekend, two limited-release movies debuted in a handful of urban arthouses with much higher per-theater-average grosses than the Will Smith blockbuster. The French thriller "Tell No One" and the coming-of-age drama "The Wackness" proceeded to roll out through the summer and, more important, find their audiences. Not many others did.

The release-date game, then, remains a cross between 3-D chess and a high-stakes poker game, with ticket-buyers passively looking on. For all the bluffing and sword-rattling, eventually all studios must find a date for all movies.

Just as long as it's not Nov. 19, 2010. That's when "Harry Potter and the Deathly Hallows, Part I" is slated to open.

Ty Burr can be reached at tburr@globe.com. For more on movies, go to www.boston.com/movies.