As of right now, about 35 minutes ago. You can also check by browsing https://www.reddit.com/r/AskHistorians/comments/

As for the top upvoted threads about 12 hours ago or 24 hours ago.

About 50% of all questions get answered and in case of the top upvoted ones the percentage is even higher (cracking 80%). Answers do, however, need time so you can use remindme bot or check back later for an answer.