Here I have written a very brief post about the release date and general inability to assess it correctly. As a constant reader of the business literature, I thought how the same paragraph would look like if it were a part of a business book.
When you set a release date for a software product, you perfectly understand that the actual date will be at least six months from the declared. But you still want to declare it as soon as you reasonably can because there is a trick there. No matter what date you state, the release will always be six months away from it. This way postponing the declaration does not help with the more accurate projection while certainly delays the release.