@Forgoodnesssakemeagain this is so frustrating - I get this as well. DH will swear something’s on Tuesday when it’s in 4 different types of calendar as a Thursday etc.
The way I approach it is just not to argue about what he ought to know, or what I know we agreed, or what is in the calendar, just stick to making sure the plans are as clear as possible now.
The memory issue won’t change. And in the case of my DH he doesn’t understand the scale of the problem, because he is convinced he remembers things perfectly well. So to be corrected about things he doesn’t realise he doesn’t remember is invariably experienced by him as criticism or gaslighting.
I try not to focus on the issues in communication & memory because that just leads nowhere. It won’t change, he just feels attacked, we haven’t been able to find a way to collaborate on practices that might help him remember.
I just very neutrally say, oh, it’s 6, not 7. I’ll send you a reminder text an hour before. <big smile>
And then just hope his phone is charged / he can find his phone.
It is so frustrating, and I can’t count on him. But treating this as something we could get to the bottom of, and work towards improving as a couple just led to endless conflict and misery. Now I just organise my own life in the understanding that I can’t count on him, and that his involvement with things is more likely to be an obstruction than a help.
It doesn’t feel great, but life works more smoothly, and I’m not so much of a hostage to his chaos. We get along better day to day when I’m not constantly banging my head against the brick wall of things that won’t change. I arrange things to make sure he is not in a position to let DC down my forgetting things, as that is the top priority really.