TeutonicNights is right. It wouldn't be called "stardate" if it was the simple Earth date. Because it simply is no friggin' STARdate then. The name itself implies that it's more complex and based on some interstellar time, and not on the time it takes some planet to orbit its sun.
I believe this image sums it up nicely.
Really? What is the true spirit of TOS?
C'mon now.. Do you really expect me to define it for you??
What BBS are you a member of?
Please, I'd like to know.
The spirit of TOS? Fun and adventure with, maybe, some philosophical/allegorical undertone every once in a while if the writers thought to put it in.