tzdata for Switzerland 1940 - 1942 probably incorrect

[Alois Treindl]

Hello

tzdata currently has these rules for Switzerland:
# From Whitman (who writes ``Midnight?''):
Rule  Swiss   1940    only    -       Nov      2      0:00    1:00    S
Rule  Swiss   1940    only    -       Dec     31      0:00    0       -
# From Shanks & Pottenger:
Rule  Swiss   1941    1942    -       May     Sun>=1  2:00    1:00    S
Rule  Swiss   1941    1942    -       Oct     Sun>=1  0:00    0       -

These are most likely incorrect. I have been practicing astrology in 
Switzerland since 1980 (in recent years running the website 
www.astro.com) and have never come upon any source which claimed DST in 
Switzerland for 1940.

A current source is for example metas.ch/metasweb/Themen/sommerzeit;internal
which is the Federal office for meteorology.

This page has (near the bottom)
Sommerzeit 1941 bis 1942
Bei Beginn wurden die Uhren von 01:00 auf 02:00 Uhr vorgestellt und am 
Ende entsprechend von 02:00 auf 01:00 h zurückgestellt.
(begin at 1 am, clocks shifted to 2am; end 2am, clocks shifted to 1 am)
1942  begin 4. Mai  end 5. Oktober
1941  begin 5. Mai  end 6. Oktober

This is what Shanks has in the International Atlas, all editions. He is 
wrongly quoted in tzdata. 5 may 1941 is a monday, 6 Oct 1942 is a monday.
4 may 1942 and 5 Oct 1942 are also mondays.
The rules must either be changed to
Rule  Swiss   1941    1942    -       May     Mon>=1  2:00    1:00    S
Rule  Swiss   1941    1942    -       Oct     Mon>=1  0:00    0       -
or made explicit for these two years, 1941 and 1942.

The rule for 1940 must be deleted.

Best regards

Alois Treindl

-- 
|| Dr. Alois Treindl,  Astrodienst AG,  mailto:alois at astro.com
|| Zollikon/Zurich, Switzerland
|| Free astrological charts at      http://www.astro.com/
|| SWISS EPHEMERIS Free Edition at   http://www.astro.com/swisseph/