Yes, I was surprised in my forties to notice that (for me) this is strangely important. In my calendar I keep "deathdays" as "//persons_name" and when I do, I am thinking of the "//" as "Signed out".

I'm not sure that, beyond my own thoughts, I give more or less attention to these as opposed to living person's birthdays, but I deeply honor it as my way of acknowledging and more importantly, not forgetting that this [un-birthday] changed my life.