There are no TimeZone IDs for London or Paris (BST, WET).
There need to be two SimpleTimeZones that reflect
the Unix "GB"/"GB-Eire" and "WET" TZ settings.

Here is the time now:

% env TZ=GMT date
Wed Apr 29 01:20:15 GMT 1998
% env TZ=WET date
Wed Apr 29 02:20:23 WET DST 1998
% env TZ=GB date
Wed Apr 29 02:20:28 BST 1998


But look at what TimeZones are available:

[...]
BET (Apr 28 22:20 GMT-03:00) -180 minutes (-3 hours). USES DAYLIGHT IN STANDARD
CAT (Apr 29 24:20 GMT-01:00) -60 minutes (-1 hours). USES STANDARD ALWAYS
GMT (Apr 29 01:20 Greenwich Mean Time) 0 minutes (0 hours). USES STANDARD ALWAYS
UTC (Apr 29 01:20 GMT+00:00) 0 minutes (0 hours). USES STANDARD ALWAYS
ECT (Apr 29 03:20 Central European Daylight Time) 120 minutes (2 hours). USES DAYLIGHT IN DAYLIGHT
EET (Apr 29 04:20 GMT+03:00) 180 minutes (3 hours). USES DAYLIGHT IN DAYLIGHT
[...]

There are no TimeZones (even strangly named ones) that reflect
the correct behavior.