Kyle Hill:
You’ll hear any reputable Star Wars fan point it out eventually: Han Solo’s famous boast that the Millennium Falcon “made the Kessel Run in less than 12 parsecs” may have sounded impressive, but from an astronomical perspective, it made no sense. A parsec is a unit of distance, not time, so why would Solo use it to explain how quickly his ship could travel?
There are two stories going on here. The first is that Solo’s famous line of dialog was simply a mistake of terminology. The second — the one I choose believe — is far more interesting, because it means that when Obi-Wan sat down across from the wryly smiling Han Solo in that cramped cantina, he met a time-traveling smuggler born at least 40 years before the events of The Phantom Menace ever took place.
Sadly, @JayRay is probably right about Han just wanting to sound impressive.