"I only make the distinction because, throughout this 50th anniversary year, I have often had to remind myself to use "commemoration" rather than "celebration" - I've been pulled up a couple of times on the concept of celebrating someone's death!"
Oh, in the end I can't resist. What we are "celebrating" is the anniversary, not the death. Commemorating an anniversary makes no linguistic sense. And as someone else said, we are celebrating a life - only an eccentric would think we were celebrating a death.
The Yorkshire Polymoth