The stardate system should have been thought out and designed properly before they went on the air. In TOS it doesn't have any systematic sense it in, except that the numbers get higher as the series goes along.
Then in TNG, stardates started with the number 4 to reflect the 24th century, but the next digit marked the show's season number. So in spinoffs beyond year 10, the stardates begin with 5. Again, it doesn't make good sense.
The original series did have a thought-ought star date system. The problem is that (a) episodes were frequently aired out of order and (b) writers regularly ignored the star date system set up by the show, and revisions suggested by de Forest Research to keep the numbers in line were not always followed.