Originally Posted by FangsF15

You do not have to bid reserve on 1 Nov. He can absolutely bid an X day on 1 Nov, thereby leaving the 31st as a single day of reserve, and is not usable until 1000 at the earliest.

If the 1st is not an X day (coverage award, for example), only then do reserve bidding rules do apply (3-99-5 or 4-99-4).