icalendar devel - Aug 2008 - Question about Timezone In 1.0.2

I''m looking at the docs for 1.0.2 and saw this example...

  # Now, you can make timezones like this
  cal = Calendar.new
  cal.timezone do
    timezone_id             "America/Chicago"

    daylight do
      timezone_offset_from  "-0600"
      timezone_offset_to    "-0500"
      timezone_name         "CDT"
      dtstart               "19700308TO20000"
      add_recurrence_rule   "FREQ=YEARLY;BYMONTH=3;BYDAY=2SU"
    end

    standard do
      timezone_offset_from  "-0500"
      timezone_offset_to    "-0600"
      timezone_name         "CST"
      dtstart               "19701101T020000"
      add_recurrence_rule   "YEARLY;BYMONTH=11;BYDAY=1SU"
    end
  end


I added that exact bit of code to my program, but all I get in my ICS file is
this...

BEGIN:VTIMEZONE
TZID:America/Chicago
END:VTIMEZONE


None of the daylight or standard information is added in my ICS file.  Am I
missing something?

Thanks,
Matt