Hard coding a data object and using your code works for me. Maybe try that to narrow it down? Or try deleting the Date Picker element and re-adding. I’ve had that strangely work in the past.
let data = {
individual : {
dateOfBirth : 'Fri Jan 13 2017'
}
}
if(data.individual.dateOfBirth){
console.log(data.individual.dateOfBirth); //'Fri Jan 13 2017'
console.log(typeof data.individual.dateOfBirth); //string
const date = new Date(data.individual.dateOfBirth);
console.log(date); //object --> Date printed properly for default date object
console.log(date.toDateString()); //'Fri Jan 13 2017'
$w('#dateOfBirth').value = date; //Datepicker shows 01/13/17
}