Back to the Future Day

Rico says that would be 21 October 2015, the date to which Marty McFly and Doc Brown time-travel in 1989’s Back to the Future Part II. 

Susie Poppick has a Time article about what predictions they got right:

While we haven’t made much progress toward levitating autos, controller-less gaming and several of the film’s other predictions have indeed come to fruition—and many others are, at least, very close. (Robot chefs will go on sale in 2017, and Chicago Cubs fans may still have a shot, however slim, at World Series tickets.)

Here are ten Back to the Future II inventions that are available for purchase today:

1. Personal DronesFlying drones are ubiquitous in Back to the Future’s 2015, and they’re shown doing everything from walking a dog to capturing images for news organizations.
The latter prediction has come true, and while people still walk their dogs the old-fashioned way, drones—widely available to consumers for about $1,000 a pop—have given us new and creative ways to catch fish, deliver dry cleaning, and make people feel awkward at holiday parties.
2. Tablets and Mobile Payment technologyViewers catch a glimpse of a flat, wireless electronic device in the film, during a scene in which an elderly Terry asks Marty to electronically donate a hundred dollars— equal to only a couple of inflation-adjusted 1985 dollars— to save the town’s historic clock tower.
Thankfully, inflation hasn’t hit the dollar nearly as hard as Back to the Future predicted. But mobile technology has met and even surpassed that of the devices in the movie, in a way that one of the film’s screenwriters recently said he never could have imagined.
The film’s prediction that wireless devices could be used for payment (in cabs, for example) was spot on, and in the last decade we’ve seen the advent of smartphone apps like Venmo, Apple Pay, and Square, which make it easy to exchange cash electronically. Some even use fingerprint recognition, just like in the movie.
3. Biometric devicesFingerprint recognition is used throughout the film, but one key scene occurs when Marty’s girlfriend (and future wife) Jennifer uses her thumbprint to open the door to her house in 2015.
Indeed, today fingerprints and other biometric measures are used to unlock devices like the iPhone, view bank account information, and even open the door to your home.
Unfortunately fingerprint theft is also a problem today, as the movie predicted, though thieves don’t need to cut off victims’ thumbs to steal their prints.
4. Hands-free gaming consolesIn one memorable scene, which takes place at the nostalgic Cafe ’80s, two young boys are taken aback when they see Marty play an arcade game. “You mean you have to use your hands?” one says. “That’s like a baby’s toy!” the other scoffs.
While plenty of video games still require the use of your hands, it’s been five years since Microsoft launched the Xbox Kinect, which lets gamers control onscreen actions using voice and gestures. Similar technology used for computing and managing a smart home is also becoming a reality thanks to innovations by Apple and Amazon.
5. Smart clothing and wearable technologyMarty wears power-lacing sneakers and a size-adjusting, auto-drying jacket in the film, two inventions that haven’t appeared yet, though rumors are swirling that Nike has plans to launch real auto-lacing shoes this year. (Alas, while movie fans can buy limited-edition 2011 light-up Nike Mags on eBay, those are more superficial replicas: They don’t have working power laces.)
What is available today are a host of wearable technology products, including wristband fitness trackers like the Fitbit, “smart shirts” that measure breathing, heart rate, and sleep patterns, and infant-size onesies that double as baby monitors. And while they may be too early-stage for purchase, other inventions like stain-proof clothes and high-heels that change color with the click of an app are under development.
6. Video PhonesMarty’s future self gets fired during a video phone call in Back to the Future II. That call is not only prophetic of video chat applications like Skype and Apple’s FaceTime, but also of Facebook, in that personal details like date of birth, occupation, political leanings, and hobbies are shared electronically.
Of course, the movie gets a few big details wrong, like the widespread use of fax machines.
7. Waste-Fueled CarsAlthough you can’t yet buy a vehicle with a fusion engine, like that in Doc Brown’s DeLorean, the scene in which Doc uses garbage to power his car (well, technically the flux capacitor) is prescient.
In fact, Toyota is promoting its new hydrogen fuel cell car— the Mirai— with an ad campaign featuring Back to the Future actors Michael J. Fox and Christopher Lloyd.
Hydrogen-powered cars are lauded as environmentally friendly, since they convert hydrogen and oxygen to electricity, with water vapor as a byproduct. That eco-friendliness is partly offset by the fact that fossil fuel or natural gas is typically consumed to create the hydrogen in the first place, but scientists are experimenting with solar and wind-powered generation and, in Orange County, California, hydrogen will be harvested from human waste.
8. HoverboardsWhile you can now buy hands-free scooters that are widely described as “hoverboards”, they technically don’t count, as they have wheels and don’t actually hover off the ground.
That said, startup Arx Pax has successfully created a working, real-life hoverboard called the Hendo, which pro skateboarder Tony Hawk has personally tested. Lexus has also created a hoverboard, using a different technology involving superconductors. Unfortunately, both versions can glide only over conductive surfaces, so you probably won’t be using one to escape bullies in your town square any time soon.
Note: if you care more about form than function, you can buy a (non-hovering) replica of the pink Mattel board that Marty “borrows” from a little girl.
9. Video GlassesSadly, Princess Diana never got a chance to become Queen, as the movie predicted. One correct prediction from the film’s vision of 2015 is how personal technology would disrupt the American dinner table. In one scene, Marty and Jennifer’s future kids ignore their families, instead watching television and talking on the phone using futuristic glasses. Sound familiar? Though smartphones are the real source of distraction today, high-tech video goggles keep getting more advanced and popular. Google has stopped selling Google Glass (at least for the time being), but pairs are available for purchase on eBay and can be used to watch streaming video, record images, and search the internet.
10. Pepsi PerfectPepsi Perfect celebrated the thirtieth anniversary of Back to the Future with a replica Café 80’s space at New York Comic Con. This one is a marketing stunt, though hardcore fans might not mind: in honor of the trilogy’s thirtieth anniversary, Pepsi is selling a limited number of bottles of Pepsi Perfect, the soda of choice in Back to the Future‘s 2015. The bottles, sold in the movie for fifty dollars, will cost $20.15 (get it?) if you order them online, though cosplayers got bottles for free at ComicCon.
Despite the futuristic packaging, the flavor of Pepsi Perfect is traditional; the company is using natural cane sugar rather than the typical corn syrup. Unfortunately, that doesn’t make it any healthier.

Rico says predicting the future is always hard; see examples here. (But Pepsi made with cane sugar? Not as good as a Mexican Coke, but at least they're trying...)