a bit after he finishes a day's work in the evening. this kind of gift not only proves that you usually have concerned about your father's daily life, but also gives him a favorite gift in that special day. also you can buy any other thing he likes, such as watch, tie and so on.
a good dinner made by you would be another good choice. in other days, you may be too busy to eat with your father. i promise that cook him a nice dinner on father's day can be a great surprise for him. do not hesitate, just do it!
also, you can go out with him on that 