It looks like I found a bug in the way WordPress handles the Post Timestamp functionality. If I edit an item which had a time stamp in the future and change it to another date the post still goes live on the original date - not on the new one I specified.
See the two latest posts in my blog: http://dmitrysotnikov.wordpress.com
Today is July 19, this was their originally intended date, which I later changed to July 20 (tomorrow). Despite this change both of them went live today - 1 day early.
Ironically, despite the fact that the posts went live 1 day earlier, both their paths and their Published date have July 20 (the date which I set later and wanted them to go live):