code: func WmUserTimeWindowSet(xu *xgbutil.XUtil, win xproto.Window,
  	timeWin xproto.Window) error {
  
  	return xprop.ChangeProp32(xu, win, "_NET_WM_USER_TIME_WINDOW", "CARDINAL",
  		uint(timeWin))
  }
docs: // _NET_WM_USER_TIME set