Quoting the announcement blog post from August 19th:
This contest will be going on for the next two weeks starting Monday the 29th at 00:00 UTC!
The 29th was five days ago.
The announcement both stated next two weeks and August 29th, which doesn't match. But still, exact date and time (and time zone) trumps the rest of the sentence IMO.
Today, on the SU home page:
The Super User 2nd anniversary contest ends Sunday! Cast your final vote for the Most Valuable Super User and submit your blog posts now.
This is tomorrow.
This might have been the shortest two weeks I have ever experienced. This will be a surprise for folks aiming for the prizes, for example, I can imagine more blog posts coming next week.