We’ve discussed the timing of the ban many times before here. Article 10.11 of the Code does say that the ban begins at the time of the final decision, but if there have been delays in getting to that point which aren’t the athlete’s fault, the ban can be back-dated to the time of the positive (10.11.1).
What if the delays are the athlete’s fault? Can’t Froome take advantage of this to drag out the hearing? No. Article 10.8 says that all results from the time of the positive are DQd, “unless fairness requires otherwise.” If Froome intentionally stalls, fairness does not require that the ban begin at the time of the final decision.
It’s easiest to illustrate with an example. Suppose Froome drags out the process till after the Tour, and gets a nine month ban in August. The nine months begin in August, but in addition, all of his results from the Vuelta last September though August of 2018 are disqualified. So in effect, he gets a ban of more than a year and a half. The additional time is in effect a penalty for delaying the case.
If Froome were not responsible for the decision’s being delayed till August, then in that case the ban would still be back-dated, per 10.11.1. So his nine months would go till June, and probably he could keep the Tour results. The bottom line, though, is that if Froome rides the Giro/Tour and is sanctioned later, he can’t keep those results unless the suspension is so short that even back-dated it’s finished before the start of the Giro or Tour.