DH wrote a letter to DCs school, stating that DS1 will need to leave at 1330 today for a medical appointment.
The appointment is tomorrow at 1330, for DS1s first CAMHs appt- for fucking anxiety.
He rang the school when he realised his mistake but it didn't get through to DS1, who was ready to go this afternoon and no one turned up. 
I have repeatedly said it is on Thursday, it is also on his phone calendar and the wall calendar, he said he forgot what day the appointment was on.
So AIBU to be pissed off he didn't bother to check the details?