code: private Date seasonalDateFromIcs(String icsFileName, String eventSummary, int year) {
      Map<Integer, Date> dates = getDatesFromIcs(icsFileName, eventSummary, year, year);
      return dates.get(year - (eventSummary.equals(Holiday.NEW_YEARS_EVE.getSummary()) ? 1 : 0));
    }
docs: Finds and returns the date for the given event summary and year within the given ics file,
  or null if not present.