code: function tick(frameTime){
  
      let newFrameUnixTime = utils.getUnixTimeInMilliseconds();
      if (frameTime)
          frameDuration = frameTime;
      else
          frameDuration = newFrameUnixTime - frameUnixTime;
      
  
      // dont consider frame duration if app is not active
      frameDurationClone = appActive ? frameDuration : 0;
  
      frameUnixTime = newFrameUnixTime;
      timeSinceStart += frameDurationClone;
  
      if (appPlaying){
  
          playTimeSinceStart += frameDurationClone;
          
      }
  
      if (videoPlaying){
  
          videoDuration += utils.convertMillisecondsToSecondsFloat(frameDurationClone);
  
      }
  
  }
docs: Updates the application timings.
  Calculates frameTime as the difference of current
  frame time and the previous frame time. In case app was not active the previous frame,
  sets the frame time to 0. Correspondingly calculates timeSinceStart and
  playTimeSinceStart
  @memberof TimeManager
  @param {number} frameTime specify the frameDuration if known [optional]