Assuming that the reservation is on points, then if you cancel 31 or more days before, then there is no penalty and the points go back into your account. However, dependign upon how close you are to the end of your UY, it may be too late to bank the points.
If you cancel 30 days or less before the start of the vacation, then the points go into a holding account. The points in a holding account can only be used within 60 days of the proposed new trip and they will be lost at the end of your UY.