This will be fixed in 188.8.131.52.
As ArtOfCode correctly surmised, your phone is trapped in a localized temporal distortion field causing it to see responses from the server before they are sent... or something.
The problem is we have a single method for stringifying dates
toRelativeTime() and this method sometimes has to shorten future dates like bounty expirations or upcoming events. When it sees your post from the future, it assumes it's that kind of thing.
Because we can be reasonably sure that posts shown in the app have to have been posted in the past, I've changed the method to
toRelativeTimeIncludingFuture(_:Bool) and will show "just now" for future posts, comments, etc.