code: def ValidateFeedStartAndExpirationDates(self, problems, first_date, last_date,
                                            first_date_origin, last_date_origin,
                                            today):
      
      warning_cutoff = today + datetime.timedelta(days=60)
      if last_date < warning_cutoff:
          problems.ExpirationDate(time.mktime(last_date.timetuple()),
                                  last_date_origin)
  
      if first_date > today:
        problems.FutureService(time.mktime(first_date.timetuple()),
                               first_date_origin)
docs: Validate the start and expiration dates of the feed.
         Issue a warning if it only starts in the future, or if
         it expires within 60 days.
  
      Args:
        problems: The problem reporter object
        first_date: A date object representing the first day the feed is active
        last_date: A date object representing the last day the feed is active
        today: A date object representing the date the validation is being run on
  
      Returns:
        None