When Marty McFly travelled to the future in the 1989 "Back to the Future" sequel - to October 21, 2015, to be precise - he was greeted by flying cars, self-tying sneakers and hovering skateboards.

The futuristic items were from a distant world for the time-travelling teenager on a journey from 1985 to 2015 to save his children.

But that day finally arrived on Wednesday, dubbed "Back to the Future Day" as fans of the blockbuster trilogy around the world celebrated the movie milestone.

Social media sites were ablaze with talk about the sci-fi adventure, cinemas held special screenings of the film and companies jumped in on the hype with savvy adverts.

In a commercial for Toyota, Michael J. Fox and Christopher Lloyd, who played the much-loved McFly and Dr Emmett "Doc" Brown, reunite on screen to discuss which predictions "Back to the Future Part II" got right.

While the so-called hover boards have yet to make their commercial debut, other gadgets such as wearable eye glass screens and video calls have turned out closer to the mark.

"We've got 3D movies," Lloyd says as the two actors sit in a diner. "We've got fingerprint technology," Fox answers.

Other companies have also joined in.

Pepsi unveiled a limited run of "Pepsi Perfect", the soda McFly drinks in the film, while Nike, whose power-laced shoes the character wore, tweeted Fox on Tuesday saying "See you tomorrow", leaving fans speculating over the message.

An article in Britain's Guardian newspaper, meanwhile, suggested that fans might be seeing the forest for the trees.

"The world ... is full of millions of idiots complaining about the lack of hoverboards via hand-held devices that are connected to the sum total of the history of human knowledge," it said.

Fox and Lloyd are due to make an appearance at a special New York screening of the film and a 30th anniversary Blu-ray and DVD of the trilogy is being released to mark the occasion.

Some fans had hoped for a revival of the franchise at a time when others movies are getting reboots. But earlier this week, one of the films' executive producers said a fourth instalment was unlikely.