@Test
  // 1000000 times: 627 mills.
  // 1000000 times: 628 mills.
  // 1000000 times: 631 mills.
  public void begTimeOfDate() {
    Calendar calendar = CalendarHelper.today();
    Calendar begTime = null;
    Calendar endTime = null;
    int count = 1000000; // 100w
    long beg = System.currentTimeMillis();
    for (int i = 0; i < count; i++) {
      begTime = CalendarHelper.begTimeOfDate(calendar);
    }
    //
    long end = System.currentTimeMillis();
    System.out.println(count + " times: " + (end - beg) + " mills. ");
    //
    System.out.println(CalendarHelper.toString(begTime));

    beg = System.currentTimeMillis();
    for (int i = 0; i < count; i++) {
      endTime = CalendarHelper.endTimeOfDate(calendar);
    }
    //
    end = System.currentTimeMillis();
    System.out.println(count + " times: " + (end - beg) + " mills. ");
    System.out.println(CalendarHelper.toString(endTime));
  }