My dad thinks the calendar in the house is wrong. He sees that it's 19 August, but if there are no appointments or notes written on the entry he thinks the calendar is faulty,
Mum explains to him that they have no appointments on that date and then shows him the next date when there is an appointment or outing (eg 23 August). It doesn't register and he becomes stressed and angry towards my mum for not having the "right" calendar.
Any advice would be gratefully appreciated.
I do think that might help, Kym; but I would add that the feeling that one ought to be somewhere else or that one has forgotten something important is sadly very common in people with dementia, and isn't (of course) based on anything rational. I wouldn't suggest adding fictional activities, but as well as marking days as free she might consider noting in the calendar whatever they are doing just around the house: valet car, grocery deliveries, garden project - just something, to show what that day involves.
How is your mother managing overall? Does your father go out to a day centre, does she have any help with keeping him occupied?
I would be telling Dad about the cat's eye doctor appointment and Dad would think the appointment was for him, etc. Now I don't mention any doctor appointments at all. Dad didn't want to miss an appointment or to be late.