bentime.js

if('registerElement' in document) {
  var BenTime = Object.create(HTMLElement.prototype);

  BenTime.createdCallback = function() {
    var stamp = parseInt(this.getAttribute('stamp'),10)
    var delta = Math.abs(stamp - new Date)
    var s = ~~(delta / 1000)
    this.innerHTML = s + 's'
  };

  document.registerElement('ben-time', {prototype: BenTime});
}