/**
 * subtractDateFromDate
 * Use the millisecond value insert both elements to calculate a new date.
 * @param d1 {Date}
 * @param d2 {Date}
 */
function subtractDateFromDate(d1, d2) {
    return new Date(d1.getTime() - d2.getTime());
}
/**
 * addDaysToDate
 * Create a new Date based on the milliseconds of the first date,
 * adding the milliseconds for the extra days specified.
 * Notice that days can be a negative number.
 * @param d {Date}
 * @param days {number}
 */
function addDaysToDate(d, days) {
    var oneDayInMilliseconds = 86400000;
    return new Date(d.getTime() + (oneDayInMilliseconds * days));
}