Some times tasks don’t have specific deadlines, or they don’t have one when you are creating them. In this case, you can make it a “Someday” task.
To set a task as Someday, simply type a question mark (“?”) in the due date box.
Once you save this task item, you should be able to see in the due date column that this task is labeled as “Someday”.
Someday tasks will show up under All Tasks -> Someday section, as well as the Today view -> Someday Tasks list.