Shedding of velvet comes fairly fast on the heels of the end of antler growth, but there could be several weeks separating the two events, or only a few days. The velvet doesn't begin to dry up until the supply of blood and nutrients begins to wane, which is technically the end of antler growth. The exact date of these events may vary by as much as a month or more between individual deer, depending on nutrition, micro-environment, and genetics. The cycle of antler growth is triggered, or regulated, by changes in the hours and minutes of sunlight in a day in every animal.
Hope that helps.