A good apology leaves the other person room to stay mad for a while.

A real apology hands over control of the timing. If you say it and then wait for immediate forgiveness, you have turned the moment into a request, and the other person has to manage your feelings on top of their own. Letting them stay angry for a while is the part that proves you meant it. Their anger is theirs, and it does not come with a deadline you get to set.

Say your part, then stop. Do not follow up the next day asking whether things are okay now. Keep behaving well in the meantime, because that is the only thing that actually shortens the wait.