You might want to use helper library like http://momentjs.com/ which wraps the native javascript date object for easier manipulations
Then you can do things like:
var day = moment("12-25-1995", "MM-DD-YYYY");
or
var day = moment("25/12/1995", "DD/MM/YYYY");
then operate on the date
day.add('days', 7)
and to get the native javascript date
day.toDate();