The year 2015, as depicted in the film, features such items as colander hats and Hoverboards. (It also has the Chicago Cubs, who are currently battling the New York Mets in the NLCS, winning the World Series.)
Shortly after midnight on Wednesday, the official Back to the Future Facebook page shared a special message from Doc Brown (Christopher Lloyd) about today's significance.
"The future has finally arrived. Yes, it is different than we all thought. But don't worry, it just means your future hasn't been written yet," Brown, ever the wise one, tells us.
Check out the full message below. How are you celebrating Back to the Future Day?