“Light-year” is always a measure of distance rather than of time; in fact it is the distance that light travels in a year. “Parsec” is also a measure of distance, equaling 3.26 light-years, though the term was used incorrectly as a measure of time by Han Solo in Star Wars.
Please, Star Wars fans, don’t bother sending me elaborate explanations of why Solo’s speech makes sense; I personally heard George Lucas admit in a TV interview that it was just a mistake.
BUY THE BOOK!