How long can someone be mad?

My dad is ignoring my mom because he thought she was smiling at him when he was choking on water when clearly she wasn't. He totally made that up and I think he believes it himself. He's been mean and ignoring my mom for a week (he didn't hit her or anything he's just being rude and nasty). I figured today he would talk to my mom cuz we just found out his uncle died so my mom told him and he just says oh and goes back to ignoring her. And I know he's thinking of some plan to get revenge or whatever. I'm just sick of it. Stuff like this happens almost seasonally which I just don't understand. If he's been normal for too long you know something like this is coming.