code: protected Calendar getStartOfDayJavaCalendar (final long timeInMillis)
    {
      final Calendar startOfDay = createJavaCalendar (timeInMillis);
      startOfDay.set (Calendar.HOUR_OF_DAY, 0);
      startOfDay.set (Calendar.MINUTE, 0);
      startOfDay.set (Calendar.SECOND, 0);
      startOfDay.set (Calendar.MILLISECOND, 0);
      return startOfDay;
    }
docs: Returns the start of the given day as a <code>{@link Calendar}</code>. This
  calculation will take the <code>BaseCalendar</code> time zone into account
  if it is not <code>null</code>.
  
  @param timeInMillis
  A time containing the desired date for the start-of-day time
  @return A <code>{@link Calendar}</code> set to the start of the given day.