def get_value(format=CFDate::TIMESTAMP_UNIX)
      if(format == CFDate::TIMESTAMP_UNIX) then
        @value.to_i
      else
        @value.to_f - CFDate::DATE_DIFF_APPLE_UNIX
      end
    end
def get_value(format=CFDate::TIMESTAMP_UNIX)
      if(format == CFDate::TIMESTAMP_UNIX) then
        @value.to_i
      else
        @value.to_f - CFDate::DATE_DIFF_APPLE_UNIX
      end
    end
get timestamp, either UNIX or Apple timestamp