[gmac]

Right — and it could perhaps default itself to the date you joined, since that's a moment when it seems likely you liked what was on offer.

[Aachen]

That does introduce the risk that people actually use this. Now, this page is a gimmick, a historical artifact. If it were actually used by more than a handful of users, that would be right alienating for new users, especially if it's a fixed date that you have to manually update.