code: function(started_time) {
  
  		var now = new Date().getTime();
  		this._started_time = started_time || now;
  		this._end_time = this._started_time + this._duration;
  
  		if (now < this._end_time) {
  
  			this._is_running = true;
  			Lava.Cron.acceptTask(this);
  			this.onTimer(now);
  
  		} else {
  
  			this.onTimer(this._end_time);
  
  		}
  
  	}
docs: Start animating
  @param {number} [started_time] The global system time in milliseconds when animation has started.
  May be used to synchronize multiple animations