JS Time difference between two dates.

TimeDiff.js

/**
 * Returns the amount of seconds between two given dates.
 * @param {Date} dtStart The start time.
 * @param {Date} dtEnd The end time.
 * @returns The number of seconds between the two dates.
 */
function secondsBetween(dtStart, dtEnd) {
  var diff = (dtStart.getTime() - dtEnd.getTime()) / 1000;
  return Math.abs(diff);
}

/**
 * Returns the amount of minutes between two given dates.
 * @param {Date} dtStart The start time.
 * @param {Date} dtEnd The end time.
 * @returns The number of minutes between the two dates.
 */
function minutesBetween(dtStart, dtEnd) {
  var diff = (dtStart.getTime() - dtEnd.getTime()) / 1000;
  diff /= 60;
  return Math.abs(diff);
}