We don't really have somewhere for such things.
You are right in suggesting it was raised before, and posted something somewhere at the time to the effect that it was a bit silly, not the posting as such, but the re-posting of the same thing each year. The problem being that if somebody remembers it, or thinks it's important or relevant enough, then everybody gets to know. But of nobody bothers to post, then it's forgotten and passed without mention.
I know it might be thought that telepathy is needed to know how these anniversaries are dealt with, but since I need to edit the calendar as Admin, what happens is that if someone posts such a date, I'll extract and delete the post (well, only if all it does is give the date - if it's informative, then it stays as a topic).
So, the answer is that it wasn't missed, because it is shown every year in the Scheduled Events (not my choice of name, but it's coded into the forum software) at the foot of the forum.
This shows everything we have for the coming fortnight.
Incidentally, although the mouse pointer doesn't currently change to show that each listed item is a link, clicking on it will take you to a slightly longer explanation - I've pointed this problem out, and the next version of the forum should have this omission corrected

To see the calendar and look at what we have for any other month, just hit the Calendar option at the top of the page. You need to do this for Hess, since the day is past.
To post the Hess anniversary, the 'proper' procedure would be to do a quick search in the forum for 'Hess', and then just post a reminder on that thread to bring it to current notice.
Obviously, if the search subject doesn't turn anything up, then it's time to start a new thread

Since I read everything, if a subject that corresponds to an interesting anniversary is posted, then I add it, so it's better to add an item based on its interest as a subject, which might attract more comments, rather than the date, which of itself is relatively meaningless, if that makes sense.