In Products page, select Default Settings for the product you want:
Select the Coming Soon tab and you can customize the settings under Date Format
To see the list of available date format, you can hover onto to "i" button and a list will show:
Manually type in the format into the text box. For example if you wish to show double digit form of the day (01, 02, 31, etc) , please key in [DD] into the text box:
Select Apply when ready.