The scenario I see here is that the post was created at 1:27 UTC on
December 24, it was originally scheduled as immediate, but when the
author realized the mistake he/she changed it to be December 31st.
However, the publishing itself is a separate task, so it was going out
as the change was being made. If an edit was initiated while the post
was still pending, but then we published, and then they saved the
changes, the last change with the schedule date would have been
accepted.