how to guard whether date of birth is between 18-70

[Awesome Thing]

I want to control the use birth days or user ages and I will not allow unless their age from 18-70 which will be allow to select if not i will alert a messages to him.

I have try to call Datepicker-bootstrap events but it does not show me the alert.

$('input[name=date_of_birth]').datepicker({
        format: 'yyyy-mm-dd',
        autoclose: true,
        setDate: new Date(),
        startDate: '2010-01-01',
        endDate: '2017-12-31',
        singleDatePicker: true,
        showDropdowns: true
}, function(start, end, label) {

    alert(start);
});