They’ve never been consistent in how stardates work and only really just try to make sure they run in a chronological (if inconsistent) order. I’d wave off exact translations of stardates for this reason.
But also allow for human error. I know an event which miscalculated how long they’ve been running based on failing to understand how anniversaries work, and thus have put out a whole lot of material stating they started running a year earlier than they actually did. They could have checked the archives, but didn’t.
Given how Trek is about the human condition, I think character’s messing up basic facts is as good a canon fix as “The Doctor lies” is for Dr Who.