public static DaysWindows days(int number) {
    return new DaysWindows(number, DEFAULT_START_DATE, DateTimeZone.UTC);
  }
@Test
  public void testTimeZone() throws Exception {
    Map<IntervalWindow, Set<String>> expected = new HashMap<>();

    DateTimeZone timeZone = DateTimeZone.forID("America/Los_Angeles");

    final List<Long> timestamps =
        Arrays.asList(
            new DateTime(2014, 1, 1, 0, 0, timeZone).getMillis(),
            new DateTime(2014, 1, 1, 23, 59, timeZone).getMillis(),
            new DateTime(2014, 1, 2, 8, 0, DateTimeZone.UTC).getMillis(),
            new DateTime(2014, 1, 3, 7, 59, DateTimeZone.UTC).getMillis());

    expected.put(
        new IntervalWindow(
            new DateTime(2014, 1, 1, 0, 0, timeZone).toInstant(),
            new DateTime(2014, 1, 2, 0, 0, timeZone).toInstant()),
        set(timestamps.get(0), timestamps.get(1)));

    expected.put(
        new IntervalWindow(
            new DateTime(2014, 1, 2, 0, 0, timeZone).toInstant(),
            new DateTime(2014, 1, 3, 0, 0, timeZone).toInstant()),
        set(timestamps.get(2), timestamps.get(3)));

    assertEquals(expected, runWindowFn(CalendarWindows.days(1).withTimeZone(timeZone), timestamps));
  }