'The Future' officially starts here, according to Back to the Future II - as today marks the date to which Marty McFly and the Doc travel in the sci-fi cult classic.
In the 1989 sequel, the pair - having departed from 1985 in Doc's now-iconic DeLorean at the end of the first film - arrived at exactly 4.29pm on October 21, 2015.
They were greeted by a futuristic world of flying cars and hover boards, self-drying jackets and the release of Jaws 19 - directed by Steven Spielberg's son Max, who was actually born in 1985.
The full trilogy is being shown on ITV2, starting at - when else? - 4.30pm.A special Keith Lemon Back t'Future tribute show will begin at 9pm, slotted in between sequels II and III.
A wealth of other seemingly-outrageous predictions about what life in 30 years' time would look like were made during the course of the film's visit to 2015.
Interestingly, however, not all of them were entirely off-base.
What did the film get right about the future?
The film correctly predicted the rise in the use of robots, with computerised petrol stations, non-military drones increasing in popularity and self-checkout machines in supermarkets suprisingly similar to the movie's 'robot waiters'.
Back to the Future II shows the scanning of eyes and fingerprints to check people's identities - and, indeed, biometric data is now used in this way.
It may also have provided Google with the inspiration for the Google Glass eyewear range. During the course of the film, almost every character at some point puts on high-tech specs which can magnify, take pictures and access an information database (though the source of this is never fully explained).
The advance of television was a major win for the film's creative team. As predicted, flat-screen TVs are now the norm - as are wall-filling screens and TV billboards.
The classic sci-fi movie may have even predicted the 2015 winner for baseball's World Series.
What did it get wrong?
Much of what the movie errs on is its overestimation of how much technology would advance.
While, quite rightly, the film believed automation would take off, it has not yet reached the level where we have robot dog-walkers or remote controlled litter bins, for example.
The internet, notable by its absence, is also a major sticking point for the movie's futuristic vision. In fairness, however, even cyber-experts did not realise quite how much impact the internet could have until the mid-90s.
Hoverboards - one of the most popular symbols of future advancement, as well as arguably among the most sought-after developments - are still a distant dream (although Universal Pictures did create a special ad to mark the anniversary).
We in 2015 also don't regularly enjoy dehydrated food or full-body 'rejuvenation', nor do we go from A to B in flying cars.
Perhaps most significantly - and thankfully - the movie also got fashion in the future quite outstandingly wrong.
While the film's vision of the future has not wholly materialised, fans of the movies are marking the day in the style.
An iconic scene from the 1989 film has been recreated in the city that built the famous DeLorean cars immortalised by the films.
Doc Brown's legendary zip line ride from the clock tower of the fictional town Hill Valley was staged in Belfast, where the silver gull-wing DeLorean cars were manufactured, to mark "Back to the Future Day".
Two local actors re-imagined the zip line scene, with a comic twist, at the clock tower in the Gasworks area of the city centre.
Meanwhile, events are being held across the UK to mark the day.
The National Space Centre near Leicester is hosting a Back To The Future night to celebrate the film.
Odeon will be showing the movie trilogy in selected cinemas across the UK.
There are also events across London, including:
A movie night in Greenwich at the Brooklyn Bowl - and anyone turning up in a retro costume can win free bowling and gig tickets.
The Bussey Building in Peckham is holding a ‘Back to the Future’ party called Delorean Dynamite on Friday October 23.
Maggie’s club on Fulham Road is also hosting a 'Back to the Future' party on Saturday October 24.
Other fans are holding their own parties to mark the occasion.