One of the staff would have done that.

Often people keep posting in old month topics because it is easier, or they don't realise the new month has started (or just don't care to want to start a new topic), so the staff will move the posts that appear to be from the new month and create a new acquisitions topic... with a new title created by that staffmember. (which ironically, has actually resulted in a few Ozformer award wins for people who have subsequently ended up being the first person of that newly created acquisitions topic)