C-Eur related change suggestions for version 2008e

Mon Jul 21 05:46:57 UTC 2008

In a previous email Robbin Kawabata has shown unintended changes for
the tz database relating to the change for the C-Eur Rule in 2008d. Here are
the relevant
portions of the tz database together with a few suggestions to
mend it (with + and - as the first letter of the relevant lines):

Rule C-Eur 1944 1945 - Apr Mon>=1  2:00s 1:00 S
# Whitman gives 1944 Oct 7; go with Shanks & Pottenger. 
Rule C-Eur 1944 only - Oct  2  2:00s 0 -
Rule C-Eur 1945 only - Sep 16  2:00 0 -
...
# These are for backward compatibility with older versions.
...
# Zone NAME  GMTOFF RULES FORMAT [UNTIL]
Zone WET  0:00 EU WE%sT
Zone CET  1:00 C-Eur CE%sT
Zone MET  1:00 C-Eur ME%sT
...
Zone Europe/Sofia 1:33:16 - LMT 1880
   1:56:56 - IMT 1894 Nov 30 # Istanbul MT?
   2:00 - EET 1942 Nov  2  3  :00
-   1:00 C-Eur CE%sT 1945 Apr  2  3:00
+   1:00 C-Eur CE%sT 1945
+   1:00 - CET 1945 Apr  2  3:00
   2:00 - EET 1979 Mar 31 23:00
...
Zone Europe/Budapest 1:16:20 - LMT 1890 Oct
   1:00 C-Eur CE%sT 1918
   1:00 Hungary CE%sT 1941 Apr  6  2:00
-   1:00 C-Eur CE%sT 1945 May  1 23:00
+   1:00 C-Eur CE%sT 1945
   1:00 Hungary CE%sT 1980 Sep 28  2:00s
...
Zone Europe/Belgrade 1:22:00 - LMT 1884
   1:00 - CET 1941 Apr 18 23:00
-   1:00 C-Eur CE%sT 1945 May  8  2:00s
+   1:00 C-Eur CE%sT 1945
+   1:00 - CET 1945 May  8  2:00s
   1:00 1:00 CEST 1945 Sep 16  2:00s

The problem arose because the C-Eur rules had no DST for 1945, making other
timezones free to use it without effects for 1945. However this meant that
Zone CET and Zone MET did not have DST for 1945, which is not very adequate.
I agree with the action of adding DST for C-Eur for 1945, but that means
that
other timezones using C-Eur must be changed to return status quo.

As far as I can see only Europe/Sofia, Europe/Budapest and Europe/Belgrade
are
affected, though of course Europe/Skopje and other timezones linking to 
Europe/Belgrade will be equally affected.

My suggestion for Europe/Sofia and Europe/Belgrade are to stop using C-Eur
from
1945 since the timezone abbreviation (CET) will be the same, and then only
start
CEST from the previous cutoff dates.

For Europe/Budapest the answer is easier since Hungary rule already has the
DST start time of May 1, 1945 at 23:00 encoded, so the Hungary rule can
simply
be used insted of C-Eur since 1945.

I don't have access to a zic compiler to see if the desired results crop
out, so I 
will leave that to people who can check it.

Jesper Nørgaard Welen
Email: jnorgard at Prodigy.Net.mx 
Project Leader (Líder de Proyecto) Software
CIMMYT  -  Centro Internacional de Mejoramiento de Maíz y Trigo
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