I think Wednesday October 2nd, because I think tomorrow - March 1st would be for reservations beginning on September 29 since
DVC member site is
today showing that non-home resort reservations can be made today for stays beginning on September 28 but I think I may be wrong in thinking this because what would make more sense is that tomorrow on March 1st the window would open for both September 29 and 30 since window for October 1 will open as well. Probably best to call MS again just to confirm. I am surprised that MS CM did not tell you what day to call back, that would have been better customer service on their part.
Best