How come there is a calendar for the countdown and delivery date?

The first calendar sits under the countdown section. This controls visibility of the entire delivery timer. If you are only using the delivery timer app to display a countdown and aren’t using it to display an estimated delivery date, there may be occasions you want to hide the timer. Selected dates here will achieve that. If you are displaying an estimated delivery date, the second calendar is more important to you.

The second calendar allows you to input entries that the estimated delivery date will skip. So, if you have a public holiday coming up then you will need to make sure the estimated delivery date will not land on these. By selecting the dates, the estimated delivery date will skip these and land on the next available date as per your delivery days and lead time settings. When you have “Dispatch Days” enabled, the selected dates here will skip to the next available dispatch day and the correct delivery date will be output based on that.