Keep in mind this isn't an exact science, as not all science fiction films are as meticulous as Back to the Future with dates and times. Movies can sometimes be vague about when they're set, sometimes only providing a year. In those cases, we set the timer to count down to the month and day the film was released. It may not be canon, but it works.
As of publication, the next movie on the horizon is The 6th Day, one of Arnold Schwarzenegger's last films before assuming office as governor of California. That takes place on November 17, 2015; we are not expecting as much hubbub for The 6th Day Day as Back to the Future Day. Commonplace human cloning sounds fun and all, but a future where the XFL has thrived? A dystopia to rival 1984.
Other notable future films whose dates will arrive soon include The Dark Knight Rises in July 2016; The Running Man in November 2017; and Blade Runner in 2019.
We've also made a Twitter bot that, not only will mark the occasion when new dates arrive, but also will occasionally tweet out countdowns to upcoming milestones. We also added an update form, so if there's a title you see missing from our list, you can send it our way and we can add it.
I'm sure that in the year 3071, the hive mind once known as Jaden Smith will have some particularly opaque tweets saved for the occasion of After Earth's anniversary. Until then, however: We can't wait to see what you all have planned for The 6th Day Day!