A fairly simple idea that I think would be helpful for pretty much anybody's RP.
Make a command, ANNIVERSARIES, and when it's entered, show all the ANNIVERSARIES you have input.
Have a command to add one, where you input the date, and then you make a note next to it -- kinda like with the Ignore List, but you're not making a note for the administration but rather for yourself, and it's not next to a person's name but next to a date. Each subsequent year the date comes up, that's the Anniversary. Optionally, allow customization of the Anniversary frequency -- 1 year, 5 years, 10 years, etc. (e.g. 1 year anniversary of marriage or 10 year anniversary of entering the Discurean Outriders.)
Aside from having a command to add an Anniversary, have a command to remove an Anniversary off your list.
Have a command to activate or deactivate notification of a given anniversary. So, if you have your wife's birthday, your own birthday, your wedding anniversary and your mom's birthday but only want the system to remind you of your wife's birthday, only activate notification for that, but not for the other dates. When the Anniversary comes up, the system notifies you either by directly telling you that it's the date and showing your note for that date, or by sending you a Message if the Anniversary happened while you were offline.
There might need to be a limit to how many Anniversaries one might have, but I would recommend that limit to be generous, if it's made at all.
Thank you for reading my idea.