The amount of time will vary depending on a number of important issues such as:
1. how long ago the injustice happened (very recent and deep wounds are harder to forgive for most people);
2. how much practice a person has had in forgiving (the more the better);
3. how well one knows the pathway to forgiveness;
4. how motivated one is to forgive; and,
5. how deeply one is hurt (the deeper the hurt, the more time that is needed).
When we worked with incest survivors for one hour a week, it took on the average 14 months for most to deeply forgive. We find that it takes at least 12 weeks of hard work before a person begins to say that he or she has forgiven someone for a serious injustice.
So, be prepared for some challenging work, take breaks, and live your normal life as you do this. You may find some genuine relief in a few months. This should benefit not only you but also your father and your family.