You can edit Due Dates right within the Tasks Tab depending on your role and permissions.
To update a due date, select the Due Date hyperlink for the task you want to update. Enter a new date, or select a date using the Calendar icon. Lastly, select an option from the Update Due Dates for Other Tasks? dropdown.
Only update this task will only update the due date for the selected task.
Update future tasks will update tasks that come after the selected task. After you select Preview New Dates, you can adjust any future task’s dates by entering a new date in the Due Date field. Then select Reschedule Tasks.
Update all tasks will update all tasks that come before and after the selected task. After you select Preview New Dates, you can adjust any task’s dates by entering a new date in the Due Date field. Then select Reschedule Tasks.