There is no (portable) way to track a variable in JavaScript. Also, date information does not lie in the DOM, so you don't get the possibility of a DOM event being triggered.

The best you can do is to use setInterval to check periodically (every second?). Example:

function timeChanged(delta) {

  // Whatever

}



setInterval(function timeChecker() {

  var oldTime = timeChecker.oldTime || new Date(),

      newTime = new Date(),

      timeDiff = newTime - oldTime;



  timeChecker.oldTime = newTime;



  if (Math.abs(timeDiff) >= 5000) { // Five second leniency

    timeChanged(timeDiff);

  }

}, 500);