I think I'm missing something basic here... The Rambam, in Hilchot Kiddush Hachodesh (6:3) says that the interval between one conjunction to the next is is 29 full days, 12 hours of the 30th day, and ...
Ramba"m (Maimonedes) Hilchot Kid. Hachodesh 2:8 says: Afterwards - i.e., after [the witnesses'] testimony is substantiated - the head of the court declares, "It has been sanctified." And all the ...