This post was apparently posted at 11:08 GMT+2, which is almost two hours in the future from now.
This is obviously a bug, but is it a frontend or a backend issue?
I've noticed that I could post something at, let's say, 12PM at noon, and the post doesn't federate for some reason (possibly due to server overload either on the instance I'm using, or the instance I'm trying to post to), then I wait till 3PM and "edit" my post and change nothing except add 1 [Space] to the end of the post, and since edits cause another federation request to be sent, the post will now show up in the instance where the community is hosted, but with the timestamp appearing "Posted at 12PM", even though the instance it got sent to, never received any federation requests until 3PM, the instance never know about my post before then.
So what this means is that an instance basically just trust the timestamp of other instances. So I think what you are seeing could be some admin manipulating their instance timestamp to appear to be in the future.
Or maybe in this specific case, it's just a bug and I'm overthinking about the timestamp manipulation theory.