Help in Datepicker: How to disable default date(today) when I leave the input without value selected

Help in Datepicker: How to disable default date(today) when I leave the input without value selected

When I click on the datepicker input but not select a date and I leave the input  (click outside) , a default value is set: current date (today). 

How do I disable this? 

I've done the debbug the chrome, but could not find.