Here is some information on the Atlantis’ STS-122 launch window:
The target launch date is December, 6th. The launch Window extends just one week, so everything must go smooth in order to have a launch. The launch time for December 6th is 4:31PM EST. On successive launch attempts, the launch will be roughly 20 minutes earlier (each time).
The daily launch window extends, as usual for international space station missions, for 10 minutes. Typically, the launch is scheduled for the middle of the launch window. A 10 minute window means little contingency for bad weather, so you should expect a launch slip by a day or two in most cases. If possible, plan to have some spare days left.
Updates: