class Icalendar::Offset::TimeZoneStore

def normalized_value
  # plan b - use definition from provided `VTIMEZONE`
  offset = tz_info.offset_for_local(value).to_s
  Icalendar.logger.debug("Plan b - parsing #{value} with offset: #{offset}")
  if value.respond_to?(:change)
    value.change offset: offset
  else
    ::Time.new value.year, value.month, value.day, value.hour, value.min, value.sec, offset
  end
end

def tz_info
  @tz_info ||= timezone_store.retrieve(tzid)
end

def valid?
  timezone_store && tz_info
end