Apple assesses your app according to a set of technical, content, and design criteria to make sure it works as it should and does not contain any objectionable language or material. This can take about two weeks. AppMachine submits the app and sees the process through to its approval.
As soon as the app is approved, AppMachine ensures that it is placed in the App Store. Provided the app is submitted on time, you can tell AppMachine what date you would like to see the app appear.