When you add a date control to a screen it sets the default date to Today and if you delete that from the Default property it will show 12/31/2001 as shown below.
If you are using a data source like SharePoint, then the default will be 12/31/2001 as well. There are many reasons you might want to have blank as the default. You can do this so by setting the InputTextPlaceholder property of the date control to the following function.
If(IsBlank(Self.SelectedDate), Text(Blank()))
This checks to see if the selected date is blank (and the data source if there is one doesn’t have a value). If true then sets the place holder to blank.