In Azendoo having a Due date on a task is optional. Tasks are basically organized according to when you plan to work on them, not by when they have to be finished.
For example, you can work a full week on a document, but its target date can be for the next Tuesday.
To add a Due date on a task, simply open the task details panel, and click in the due date area to display the date picker:
Then pick the date you want:
Once the due date is chosen, you can also set a reminder
Your tasks with a Due date can be viewed from https://app.azendoo.com/#my_tasks/deadline