You could make the argument that when many of us qualified for status last year, it was based on the premise we'd earn 2x miles flown for the following year. Yes, I'm sure there was "subject to change" language in there, but it's still reducing expected benefits (for most). Technically status runs through Feb, but I'd settle for Jan 1st as a new year with new rules.
In general, the further out the better and the start of the new year is a clear delineation.