The Boxes in the Time line mode are represented as bars just like on a Gantt chart and a "top-down" mode is used for the Program Increment and Iteration levels. This means that lower level Boxes can not exceed the parent's period.
The Program Box is in manual mode which means that you can extend it or shorten it as required (currently there is no validation).
Using this mode you can do two main operation on your boxes:
The Box period is shaded yellow when adjusted (moving or resizing) using drag & drop to help you in finding the exact start and end dates. In case, when the Boxes overlap, a warning will appear:
You can drag and drop the bars to change the Box's dates when the status of the Box is other than Closed.
If a user does not have permissions to view the Box it will be shaded out.
To learn more go to Overview- Views - Hierarchy - Adding, editing and deleting boxes.