
Personally I count day one on the first day that I see blood (they are swollen for some time before bleeding.)
Having boys myself, I rely on them to tell me what day a bitch is ovulating. Which means that I don't have a wasted journey to my chosen stud.
As my girls vary so much, and don't always show the same behaviour every season, I know that one season a bitch isn't ready until day 19, and the next season it's day 8.
How far away is the boy you're using? If it isn't hundreds of miles away, I would ask him to tell you.