Defining an Activation Time of a Task 
By default a task becomes active upon its creation. You can define a different activation time by defining an offset related to the task creation time or by using an expression. The task is activated when the activation time is reached.
Prerequisites
You have opened the Process Composer perspective in the SAP NetWeaverDeveloper Studio and have expanded your project in Project Explorer view.
You have created a task.
Procedure
Expand Process Modeling, then expand Tasks.
In the context menu of a task, choose Open.
The task editor opens. The Activate this task by creating it checkbox on the Time Constraints tab page is selected by default.
Deselect the Activate this task by creating it checkbox.
The options to define an activation time different from the default one become active.
Define a new activation time by one of the following options:
Select the Use an offset relative to the task creation time radio button.
Enter a value that is greater than 0 in the Offset field.
Select a period of time from the dropdown menu.
The value in the Offset field and the period of time are added to the task creation time to form the new activation time.
Select the Use an expression radio button.
Choose the Edit... pushbutton.
The expression editor opens.
Specify an expression. For more information, see Creating Expressions.
Choose the OK pushbutton.
Result
You have defined new activation time that is different from the default one.