Default Date for Birthdate

When the date of birth is asked to the user, with a Date Picker on mobile, what should be the default date to show on Date Picker? Current date makes no sense to me as it is probably too far from the date the user has to select.

EDIT 1. I'm talking about a Date Picker on Mobile. When the users selects the date picker it needs to open in a date and then the user starts moving it. Date pickers do have a default date. I cannot have a Date Picker without default date.