How long has the dark mode existed?

[DaFace]

Among 472 "active users" (with >100 posts in the past year):

69 dark mode (15%)
17 at work (4%)
14 Royals Planet (3%)
110 "full featured" intentionally (23%)
262 "full featured" because they've just never changed it (55%)

That said, I think that's based on the actual setting in UserCP, but the drop-down in the bottom left is cookie based, so it's possible those aren't fully accurate. Still, kind of interesting to see.