Hmm... Well, Valve Corporation -the company behind Steam- is located in Washinton state in the US, so it's only around 9:00hrs PDT in the morning of September 8th there. Either, they posted the wrong release date, or maybe it will come out later today.
Aw, poor you. Hope you rest well from now on. If it doesn't come out today, maybe it'll be released on Sep. 9th PDT time. Otherwise, we can have a table-flipping party ;), since they failed to announce a change in their release date.