A stardate is a fictional system of time measurement developed for the television and film series Star Trek. In the series, use of this date system is commonly heard at the beginning of a voice-over log entry such as "Captain's log, stardate 41153.7. Our destination is planet Deneb IV..." While the general idea resembles the Julian day currently used by astronomers, writers and producers have selected numbers using different methods over the years, some more arbitrary than others. This makes it impossible to convert all stardates into equivalent calendar dates, especially since stardates were originally intended to disguise the precise era of Star Trek.