creating a multi dimensional array from a two dimensional array

this is what i have and i want to turn it into a multi dimensional array

var calculateDates = function(date1, date2) {
  var dt1 = new Date(date1);
  var dt2 = new Date(date2);
  return Math.floor((Date.UTC(dt2.getFullYear(), dt2.getMonth(), dt2.getDate()) - Date.UTC(dt1.getFullYear(), dt1.getMonth(), dt1.getDate())) / (1000 * 60 * 60 * 24));
}

var startDate = ["10 Jan 1982", "05 Mar 1990", "28 Dec 2001"];
var endDate = ["25 Jan 1982", "06 Mar 1990", "02 Jan 2002"];

var totalDays = 0;

for (var i = 0; i < startDate.length; i++) {
  var days = calculateDates(startDate[i], endDate[i]);
  console.log("Number of days between", startDate[i], "and", endDate[i], "is", days);
  totalDays += days; 
}

console.log("Total number of days:", totalDays);