In 1987, Apple released this concept video for Knowledge Navigator, a voice-based assistant combined with a touchscreen tablet computer.

Based on the dates mentioned in the Knowledge Navigator video, it takes place on September 16, 2011. The date on the professor’s calendar is September 16, and he’s looking for a 2006 paper written “about five years ago,” setting the year as 2011.

And this morning, at the iPhone keynote, Apple announced Siri, a natural language-based voice assistant, would be built into iOS 5 and a core part of the new iPhone 4S.

So, 24 years ago, Apple predicted a complex natural-language voice assistant built into a touchscreen Apple device, and was less than a month off.

(Thanks to Hugh Dubberly for the video, who helped create it for ex-CEO John Sculley’s EDUCOM 1987 keynote in six weeks on a $60,000 budget.)