Tap a Task or Dream to open its detail view. 

Note the Due date option on the page. Click on the Due date section to select a dateand select desired due date for the Task or Dream.

To delete Due date, simply click the 'X' button to the right of the due date.

* For more information about How to Edit Due Date for Multiple Goals At Onceclick here 

Additional information:

When you use the 1-Tap Planning Wizard feature, the due date for Dream is automatically set from the starting date according to the predicted duration.

* For more information about What is the "1-Tap Planning Wizard"(Plan in a Flash)?click here