Stardates were used in certain cultures as far back as the 2150s, when the United Earth government still worked with Gregorian calendar dates.
In 2154, Degra, a Xindi-Primate, sent a coded message to Enterprise NX-01 containing a stardate for when Enterprise should rendezvous with Degra's ship.
'So the stardate on Earth would be one thing, but the stardate on Alpha Centauri would be different,' Peeples says.
According to Kellam de Forest: The original script for the pilot of Star Trek was titled "Menagerie" (sic) and we in the research department, De Forest Research, didn't see it until it was in script form and came to us to review just like any other Desilu script, or any other script from any other client.T'Pol knew that it was three days in the future, indicating that Vulcans also had an understanding of stardates at that time.() Stardates did not replace clock time or everyday units for expressing larger timespans, such as days, weeks, months, years, centuries, or millennia, and tend not to apply retroactively instead of Gregorian or Julian calendars either.So we got this script, and the script originally had dates in it, like 2362, and months and days.I felt that that sounded a little awkward for the 23rd, 22nd century, so I thought that there should be another, another dating system.( In addition, Star Trek Fact Check shows a scripted narration from the same draft containing "star date 1312.6".