When you first log in you will be presented with a Service Selector. You can view a list of delivery dates for this service in either calendar view or list view.
This will load the Service and all the items available on those date(s). If a date is not available, the service you have selected is not available.
Orders made in advance for dated services like lunches and sausage sizzles, can be cancelled up until the cut-off time for that service.