@Test
 public void convertDateTimeToMilliseconds() {
   Calendar calendar = Calendar.getInstance();
   calendar.clear();
   calendar.set(2014, 1, 1, 1, 1, 1);
   final TimeZone timeZone = calendar.getTimeZone();
   long offset = timeZone.getOffset(calendar.getTime().getTime());
   Long correctResult = offset + calendar.getTime().getTime();
   assertEquals(
       highchartSeriesUtil.convertDateTimeToMilliseconds(calendar.getTime()), correctResult);
 }