The "Back to the Future" franchise is celebrating its 30th anniversary this year. Even though three decades have gone, the fans are still as obsessive and passionate about debating the plot theories and admiring the iconic DeLorean car as they were when the first part of the trilogy was released on 3, July, 1985.

There have been a number of fan films related to the franchise. Earlier this year, Robert Zemeckis, creator of the original three movies, denied any possibilities of sequels or a remake that left the fans disappointed.

However, Time has reported that a new documentary telling the story behind the movies is all set to hit the theatres next month. The documentary will be made in participation with director and co-writer Robert Zemeckis, writer Bob Gale, producer Steven Spielberg and the original cast of the movie.

"Back in Time" is all set to hit the theatres on 21 October – the same day Marty McFly (Michael J. Fox) arrived in the future in the second movie of the trilogy "Back to the Future Part II." The documentary will recount the inspiration for the original story, the decision to use the DeLorean and the impact the franchise has had in the decades since its release.

In the trailer, Spielberg says, "It really is for me inarguably the greatest time-travel movie ever put on film."

Huey Lewis, the musician behind the original movie's theme - "Back in Time" - feature in the documentary along with the theme.

"They picked the right song," Lewis says in the documentary.

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