Well, if it’s too difficult for you to tell me
DH is very strongly inclined to ask me things, rather than look them up or keep track himself. I started feeling good that i remembered things that he didn't, the novelty soon wore off. However, he had been 'trained' to know that just asking was a very, very efficient way of finding out things he didn't find particularly interesting.
So, I started to just not notice that he had asked, and so not answer, as if i genuinely had not heard his question. (If he is busy, it takes a bomb for him to notice anything so it seemed fair enough). If he kept asking, i just kept not noticing. If he took the trouble to get my attention, then ask me, I would either sound puzzled or , as if suddenly remembering, there is a copy of my schedule on the fridge (or whatever). Crucially, make no move to go and look and then go back to whatever you were doing.
He hasn't stopped asking entirely, but it has cut the volume of repeated questions considerably.
Anyone saying how difficult is it to just tell him, might usefully ask themselves why , if its so easy, he needs you to do it, while he waits for you to do it, turning a simple job into a two person event? And maybe google mental load or wifework. Pah.