The date was changed on some of the update pages in different countries to reflect the date it would be in those countries when Apple release it on the 17th in the US. Here in New Zealand we don't actually get the update until the 18th June.
It's for New Zealand, Australia and some (if not all) of Asia, because we're almost a day ahead of the United States. You guys in America will still get it on the 17th.
Oh and yeah, this is like...the 10th topic about this already...