My father has advanced Alzheimer's. Is it important to celebrate or mark milestones, like anniversaries? Or should we not since he has limited memory capacities?

Father is in a nursing home specializing in mental medical care for geriatrics. We are having 'anniversaries'. My question is, since he has limited capacities, is it important to celebrate or mark milestones, or is this just me taking my loss at 1 year anniversary? Should I make these dates special or let them alone? Part of me wants to let it go, but the other side feels he needs to be reminded. At a loss.
BobO