private void initTimeUnits() {
timeUnits = new ArrayList<TimeUnit>();
timeUnits.add(new JustNow());
timeUnits.add(new Millisecond());
timeUnits.add(new Second());
timeUnits.add(new Minute());
timeUnits.add(new Hour());
timeUnits.add(new Day());
timeUnits.add(new Week());
timeUnits.add(new Month());
timeUnits.add(new Year());