I don't know how it works but I guess that it's due to the algorithm that calculates how long ago a post was published. Let that time be p and current time c, then the time x between publish and now would be x = c - p.
Assuming that the variable c only updates once in a while, then it's possible that p is greater than c, which makes x negative, i.e. p appears to be in the future.
If that's the case, then it's not that your post will actually be published 9 minutes into the future, but rather that the system didn't check the current time since 9 minutes ago.