Dear sir/madam

On this website i find the following data:
https://www.timeanddate.com/time/zone/uk/london

2015Sun, 29 Mar, 01:00GMT → BST+1 hour (DST start)UTC+1h
Sun, 25 Oct, 02:00BST → GMT-1 hour (DST end)UTC
2016 Sun, 27 Mar, 01:00GMT → BST+1 hour (DST start)UTC+1h
Sun, 30 Oct, 02:00BST → GMT-1 hour (DST end)UTC
2017 Sun, 26 Mar, 01:00GMT → BST+1 hour (DST start)UTC+1h
Sun, 29 Oct, 02:00BST → GMT-1 hour (DST end)UTC
2018 Sun, 25 Mar, 01:00GMT → BST+1 hour (DST start)UTC+1h
Sun, 28 Oct, 02:00BST → GMT-1 hour (DST end)UTC
2019 Sun, 31 Mar, 01:00GMT → BST+1 hour (DST start)UTC+1h
Sun, 27 Oct, 02:00BST → GMT-1 hour (DST end)UTC

As you can see, the Europe/London time change rule is different every year .
But i can not find this information on yor data distribution.
https://www.iana.org/time-zones

For europe, london you give:
# Zone    NAME        GMTOFF    RULES    FORMAT    [UNTIL]
Zone    Europe/London    -0:01:15 -    LMT    1847 Dec  1  0:00s
             0:00    GB-Eire    %s    1968 Oct 27
             1:00    -    BST    1971 Oct 31  2:00u
             0:00    GB-Eire    %s    1996
             0:00    EU    GMT/BST

Maybe i do not understand how to use your data?

I put the question on stackoverflow:
http://stackoverflow.com/questions/40360032/iana-internet-assigned-numbers-authority-data-files-and-data-from-www-timeandd

regards,
--
Gintare Statkute