function (startDate, endDate, addFn, interval) {

 addFn = addFn || Date.prototype.addDays;
 interval = interval || 1;

 var retVal = [];
 var current = new Date(startDate);

 while (current <= endDate) {
  retVal.push(new Date(current));
  current = addFn.call(current, interval);
 }

 return retVal;

}