Los Angeles (E! Online) - Just call him the Crack of Dawn Knight.

Movie theaters are adding 6 a.m. opening-day showings of The Dark Knight to meet demand created by sold-out midnight and 3 a.m. screenings.

"It's normal for movies like to this start at midnight," says Chad Hartigan, a box office analyst for Exhibitor Relations Co.

But 6 a.m. screenings?

"That's not normal," Hartigan says.

There are no hard numbers for how many theaters will stay open as the witching hour turns to the rise-and-shine hour at 6 a.m. on July 18, when The Dark Knight debuts. Overall, Hartigan says he expects the movie to play at 3,800-3,900 theaters during its opening weekend.

According to Ted Hong, vice president of marketing for the online ticket service Fandango, the unusual 6 a.m. show times are indicators of unusually strong interest.

"The Dark Knight is our fastest selling film in wide release this year," Hong says. "It trumps Iron Man, Sex and the City, Indiana Jones [and] WALL-E at the same point in their sales cycles—and it's even outpacing last year's Spider-Man 3 and Pirates [of the Caribbean: At World's End]."

Per Fandango, The Dark Knight will bow dark and extremely early in midnight showings on more than 1,500 screens. (Fandango and E! Online are both owned by Comcast.)

The service says "many" of those 12 a.m. screenings are sold out in cities both expected (New York, the model for Batman's troubled Gotham City) and not (Boise, Idaho; Council Bluffs, Iowa; etc.). MovieTickets.com, another online ticketing service, reported a total of 140 Dark Knight sell-outs as of today.

In a summer led by the $311 million-grossing Iron Man, The Dark Knight has been regarded as the blockbuster to beat. A sequel to Christopher Nolan's hit franchise reboot, Batman Begins, the new movie is receiving ecstatic early reviews—Variety called it "enthralling"—and Oscar buzz for the late Heath Ledger for his performance as the seriously unhinged Joker.

As early as two weeks ago, three weeks before the July 18 debut, Fandango was reporting "dozens" of premiere-night sell-outs. As of 10 a.m. this morning, still a good eight days before B-Day, The Dark Knight was accounting for 51 percent of all tickets sold by the service. At MovieTickets.com, the film was doing more business than six of that company's Top 10 all-time hits, including The Passion of the Christ and the second Star Wars prequel, Attack of the Clones.

Says Hong: "All indicators point to [next Thursday] as a very busy night at theaters across the country."