When it comes to early showings of wannabe blockbusters, 9 o'clock may become the new midnight at the box office.

After decades of insisting that theaters wait to roll out movies until 12:01 a.m. Fridays, studios are now greenlighting shows earlier and earlier. 

“Oz the Great and Powerful” and “Jack the Giant Slayer” are two recent examples of big movies that got a very early start on their opening weekends, with both debuting in 10 p.m. Thursday shows. Warner Bros. rolled out "The Incredible Burt Wonderstone" Thursday night at 10 p.m.

Now Fox has blessed 9 p.m. Thursday screenings of “The Croods” on March 21 -- and Paramount will go with 7 p.m. Wednesday showings of “G.I. Joe: Retaliation,” ahead of its Thursday debut on Easter weekend.

"We were always going to go early with 'G.I. Joe'," Don Harris, Paramount's head of distribution, told TheWrap Thursday. "As we looked at the numbers of kids that were going to be out of school, we thought, 'why not let theaters open it for their prime shows and then play it at 10 and again at midnight if they wanted to?'"

With the box office down about 13 percent from last year, this seems as good as time as any to try something different and be aggressive in terms of going after moviegoers.

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“There really isn't a down side, other than moving out the film that's in there to make room,” Larry Collins, sr. vice-president of film for Frank Companies, which owns the 250-site Frank Theaters chain, told TheWrap. "But at that point you've already done promotion and publicity on the new one, so why not?”

Though midnight shows of one sort or another have existed for years -- think “Star Wars” and the early Batman movies -- Warner Bros. and other studios have elevated early screenings to new levels of prominence and profitability over the past decade. But such screenings were not for the masses; they were designed to accommodate the most rabid fans of the films like the “Harry Potter” and “Lord of the Rings” movies, and heighten the “event” buzz around their films.

When it works, it can pay off big-time. “Harry Potter and the Deathly Hallows, Part 2” brought in a staggering $43 million in midnight shows in July of 2011. The next three biggest midnight openings are “Twilight” movies, “Breaking Dawn, Part 1” ($30.3 million), “Eclipse” ($30.1 million) and “New Moon” ($26.3 million).

And there are other advantages to the earlier Thursday screenings for both the studios and the movie theaters. Beyond the obvious -- for most people, early showings are more palatable than midnight for a movie -- the multiplexes' cost of staffing and security go up significantly after 12, so starting earlier keeps those costs down.

“There are some practical issues that make it work," Landmark Theaters Chief Executive Ted Mundorff told TheWrap. "We have a theater in Boston, and I can't put midnight movies in there because the public transportation shuts down, and the employees would have no way to get home.”

Also, with the earlier shows, studios can have a very clear handle on how their movie will fare by end-of-day Friday, allowing them to rev up their word-of-mouth machines that much earlier. The trades report the late-night grosses the next day, and that can generate heat, too.

“That's a great thing when you have a really good movie,” Phil Contrino, BoxOffice.com editor-in-chief told TheWrap, “but when you have a bad movie....”

Another reason the studios have been willing to let theaters move the Thursday start times up is to mitigate the fallout from last year's theater shootings in Colorado. When movie attendance dipped, particularly at late shows, the thinking was that 10 p.m. screenings would be more likely to lure patrons back -- and distribution executives say it has worked.

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Of course, earlier showings complicate box-office calculations, and that's more than a nuisance for an industry that bases so many strategic decisions on past performances. Not every midnight movie is a blockbuster, and some studios have been accused of trying to inflate Friday grosses -- or at least trying to make comparisons more difficult -- with the early debuts.

“Fanboys love to flood the internet with comparisons to this film or that one,” Jeff Bock, Exhibitor Relations vice president and senior analyst, noted, “but when you open a day or half-day earlier, and you have to add an asterisk to the argument, it's not as much fun. ”

One can't help but wonder if the trend will continue, and we could see not only more openings like the 7 p.m. “G.I. Joe” bow but even earlier starts.

Fox distribution president Chris Aronson, who will be opening DreamWorks Animation's 3D “The Croods” early, told TheWrap he doesn't see a slippery slope.

“There's a limit. At some point, you might as well just open it a day earlier,” he said. While families likely won't turn out in large numbers for "The Croods" at 9 p.m., Aronson said that teenagers -- a major target demo for the film family -- very well could.