For what it's worth my Dad had been getting increasingly frustrated and cross because of his memory problems.
He said once, "I just want to know what's going on inside my head."
However once he'd got a diagnosis, vascular dementia in his case, he calmed right down. It's almost as if it's not his problem any more, because he knows now he can't help it.
One thing he finds helpful is a big A3 month to a page wall calendar.
I write his outings, appointments, timings, instructions, reminders, whatever on it so he can consult it to see what he's doing when.
We cross through each day as it ends to keep him on track with what day it is.
If you do need to correct him try to do it in a calm reassuring way rather than a negative way.
Be prepared to have the same conversation many times while he processes the information. Try and keep your tone of voice even, not irritated.
One piece of advice we were given was to get Dad out every day, don't just sit at home.
He likes going to the cinema and out for lunch or coffee. He loves people watching!
Do you have friends or family who can help support you? Don't become isolated and don't be embarrassed by his problems.
Best wishes to you both x