There’s one player who’s managed to preemptively place on the Conquest leaderboards (along with other individuals on different leaderboards). They’re finishing the conquests on Dec 31, 1999, which thus puts them ahead of everyone on the leaderboard.
The fact that he’s managed to do it multiple times makes me think there’s an exploit that’s been found.
EDIT
Now there are multiple players who have completed multiple conquests on invalid dates. And if you view their profile, you’ll see that they completed multiple conquests within seconds of each other. Given the conquests involved, this would be impossible. You cannot get Avarice and The Thrill within one second of each other, as Greater Rifts do not have gold.