Is it bad memory or does he just not listen?

It's the little things. I remember most things when I genuinely care about a person. We've been dating for a year. He claims to have bad memory but remembers many details about whatever he chooses to remember. Well he invited me to a party and I kept saying no, and he was insisting because I promised. And I let him keep it going. The party is the day of my college graduation which he has known about for the entirety of our dating and since it's in a few weeks I always talk about it. This isn't the first time he forgets something I care about and he just blames his memory but realistically he remembers a lot more than he claims to. It's just upsetting because it happens more times than not. I'll tell him something I'm