In our house, it would be a
'fuck', we have a clash, I didn't put it on the family calendar,...
'oh shit, I totally forgot that it was this weekend'
'what are we going to do'
'i can move the golf and the clubbing, but I still need to do the product launch'
'let me see if we can move the hotel and book for another weekend, I am sorry I didn't put it on the right calendar'
'I'm sorry I forget it was the same weekend'
I would walk away being annoyed that he couldn't keep more than one piece of information at a time and was so focussed on his own sphere that he completely forgot the entire evening of planning and the fact that he expects me to be responsible for the house and family admin.
DH would walk away, being annoyed that the system should have worked and he shouldn't have to remember everything as if the system worked, he wouldn't have to.
I would walk up there, or send a message, saying we have a problem... I presume the product launch has to go ahead, so what do you think, should I try to move it to another weekend, or should I go ahead with the kids, maybe you could join us for part of the weekend.