I assume the main reason why Paul Eggert wants to merge time zones is the fact there is less maintenance work, if for example EU rules change not only regarding DST, but regarding the standard time. If something like this happens, multiple zones have to be updated. Some years ago I developed my own patch to zic.c to make it understand the new keyword 'follow'. That way, I can represent a zone which deviates from a TZ "standard zone" before a certain date, and then say 'follow standard zone' at the end of the zone data. I have completed that for several countries, for example to represent the deviations from Europe/Berlin within parts of Germany before 1949, or to represent the numerous deviations in France from Europe/Paris. I attach two files which show the application of the 'follow' keyword. Of course I will be happy to share the patch to zic.c which enables it to process the follow keyword. As it is now, I apply my patch each time an update of zic.c is published. If the follow keyword is introduced into the main distribution, it could be used for zones like Europe/Copenhagen which instead of being eliminated would become Zone Europe/Copenhagen 0:50:20 - LMT 1890 0:50:20 - CMT 1894 Jan 1 # Copenhagen MT 1:00 Denmark CE%sT 1942 Nov 2 2:00s 1:00 C-Eur CE%sT 1945 Apr 2 2:00 1:00 Denmark CE%sT 1950 0 follow Europe/Berlin The information that Copenhagen is the same as Berlin after 1949 would be there, as well as the original data.