Guy Harris, thanks a lot for this analysis and the detailed descriptions of the selection processes. I forgot a /not/ in my message: "I would /not/ use one software to determine the extend of the database."
tzselect, which according to tzcode2012b/tzselect.8.txt seems to use the comments column from the zone.tab.
Yes, it does use that. Perhaps that column should be called "description" rather than "comments", so that it's not confused with "comments" in the sense of
# Lines beginning with `#' are comments.
in zone.tab. I strongly support your proposal to better distinguish between comments in the source code sense and the text in the comment field of zone.tab. Renaming the field to "Description" sounds good to me. It allows for geographic description as well as for current real world time zone information as "Moscow+00" or "Eastern Standard Time".
But for Russia (map at http://efele.net/maps/tz/russia/ ) the zone.tab data is not sufficient for the zones: Europe/Moscow Moscow+00 - west Russia Europe/Volgograd Moscow+00 - Caspian Sea Europe/Samara Moscow+00 - Samara, Udmurtia
The comments in the europe file give for Europe/Volgograd # Astrakhanskaya oblast', Kirovskaya oblast', Saratovskaya oblast', # Volgogradskaya oblast'.
Without that information mapping may fail. This information is needed.
So perhaps either
1) zone.tab needs to have something better than "Moscow+00 - {xxx}" in it
or
2) zone.tab needs more fields
or perhaps whatever *localized* databases are used by various OS's/desktop environments' time zone selection UIs needs to have more information.
The proposal at http://mm.icann.org/pipermail/tz/2012-May/017755.html would follow 1) and improve {xxx}. to have a mapping to the real world.
CN .... Asia/Urumqi most of Tibet & Xinjiang ... probably not sufficient for a "general users" user interface.
It might be good to change this to the more common "most locations", i.e. Asia/Urumqi Tibet & Xinjiang - most locations Same for America/Halifax Atlantic Time - Nova Scotia (most places),... -> America/Halifax Atlantic Time - Nova Scotia (most locations),... /and/ to specify this in the Theory file. Maybe if there is "XXX - most locations" it should be required to have at least one line "XXX - <some locations not included in most locations>" -- Tobias Conradi Rheinsberger Str. 18 10115 Berlin Germany http://tobiasconradi.com/