The Science-Fiction series STAR TREK uses an alternate Date/Time format: STARDATE.

Marginal note: Astronomers also use the word "StarTime" (or "Sidereal Time"), but this differs totally from StarTrek startime. 1 Astronomer staryear (= sidereal year) equals 365 days, 6 hours, 9 minutes and 9.54 seconds.

So far there are several definitions of calculations between STARDATES and our Gregorian Dates