You can add both start and due dates to all tasks. By doing so, you have created a task duration. This is essential if you need to have a task completed by a certain time. You can always edit the dates or entire duration of the task later.
How to Set Start and Due Dates
Just click on the start date and then on the due date. If you only select one date, this will automatically be defined as both the start and the due date. You will see the task duration on the right of the dates. Note that weekends are not included in the duration.
If you find that the date-picker is automatically selecting a duration but you only want to select a due date, double click on the date. You can also select to mark a task as urgent — this task will always appear at the top of your due tasks in the dashboard.