Sometimes Stardate references might solve continuity problems -- sometimes they create continuity problems.
Example of the former: "Catspaw" (first episode of TOS second season, and therefore the first episode to feature Chekov as a character) has a lower stardate number than "Space Seed" from season 1, which implies that "Catspaw" takes place earlier chronologically in "shipboard time". And that provides an obvious answer to the common TWOK complaint that "Khan shouldn't recognize Chekov because he wasn't there yet".
But then, there were several episodes during season 1 of TNG that were filmed when Denise Crosby was still a member of the cast, but with stardates that occur "after" Yar's death in "Skin of Evil".
In short, they're inconsistent enough to be entirely meaningless.