When I am working with the iOS Asana app, I can see the calendar view for all of the tasks I have, for example, in My Tasks. In a project or in My Tasks, I can tap to select particular calendar dates. When I select a date and then try to create a new task, the new task defaults to having no due date, and even when I try to add one, it starts with the current day (the least likely one I would actually want to assign) instead of the date that I selected on the calendar.
This functionality runs counter to the desktop web interface, where you can easily create tasks on a specific calendar day. Being able to do that is important because the due date for a task is frequently selected relative to other information on the calendar, and it can be hard to remember the particular date when the “new task” interface then boots you all the way back to present day.