after having asked around to various people working with mini-SEED data files for the better part of their lives (me included), shockingly, it seems this question has never come up before.
while the answer to the question “is it possible?” is always “yes” (knowing that a program can be written to do this), i have to wonder if it actually makes sense to make this correction, since…
without knowing what exactly your post-processing needs are, how would you know what the correct time-stamp is to apply down to the millisecond? unless the unit is actually co-located with an instrument that does have good time, i don’t think you would be able to accurately identify which data point precisely lines up with which millisecond.
as i said, i’m missing some details so can’t know for sure, but if you do have some method to identify which data point corresponds to which millisecond, a program could be written to adjust the data header time values for you. this would be work and could be provided at a cost, if you’re interested. please DM me if you would like to know more about this option.