Merlin keeps track of the following three kind of values: planned, expected and actual.

You can enter planned and actual values, expected values will be automatically calculated by Merlin. When you have a task and you enter a given planned earliest start in the inspector or the according column, you place your task on a specific start date in the time line.

Move not started activities:

If you move the Gantt chart element of a not yet started activity, Merlin will understand that you are changing the planned values, and adjusts the given planned earliest start date accordingly.

Move activities in progress:

If you move the Gantt chart element of an activity which is currently in progress (% complete
> 0%) Merlin understands that you want to specify the actual start date of the task, and changes the actual start date accordingly.

Move completed activities:

The same applies for completed tasks (% complete = 100%). Should you move their elements on the Gantt, you change their Actual Start date.