Pierre-Yves Berger found some documentary evidence of the 1894 transition in Switzerland, and I got my hands on a copy of Messerli's book, which gives more details about the circa-1855 transition. Here's a patch, which I'll push to the experimental repository. As far as data goes, this merely moves the 1855 transition to 1853-07-16.

From 9805c5c4a38750ff0c2345fdcc2a273357153259 Mon Sep 17 00:00:00 2001 From: Paul Eggert <eggert@cs.ucla.edu> Date: Wed, 11 Sep 2013 18:28:36 -0700 Subject: [PATCH] * europe, zic.8 (Europe/Zurich): Change transition to 1853-07-16.

Explain how I derived this guess from Messerli's book. Also, give better evidence about the 1894 transition, from Pierre-Yves Berger. --- europe | 39 ++++++++++++++++++++++++++++----------- zic.8 | 6 +++--- 2 files changed, 31 insertions(+), 14 deletions(-) diff --git a/europe b/europe index 8d26b4e..e70cfb4 100644 --- a/europe +++ b/europe @@ -2662,23 +2662,40 @@ Zone Europe/Stockholm 1:12:12 - LMT 1879 Jan 1 # ... the meridian for Bern mean time ... is 7 degrees 26'22.50". # Expressed in time, it is 0h29m45.5s. +# From Pierre-Yves Berger (2013-09-11): +# the "Circulaire du conseil federal" (December 11 1893) +# <http://www.amtsdruckschriften.bar.admin.ch/viewOrigDoc.do?id=10071353> ... +# clearly states that the [1894-06-01] change should be done at midnight +# but if no one is present after 11 at night, could be postponed until one +# hour before the beginning of service. + # From Paul Eggert (2013-09-11): -# Round to the nearest even second, 0:29:46. -# -# We can find no reliable source for Shanks's claim that all of Switzerland -# except Geneva switched to Bern Mean Time at 00:00 on 1848-09-12. On the -# contrary, a more-reliable source talks about "the gradual introduction of a -# national time (from the 1850s)" (Google translation) with a switch to CET in -# 1894; see Speich's review of Messerli's thesis, Traverse 1997/3, 131-3 -# <http://www.tg.ethz.ch/dokumente/pdf_files/rez_messerli.pdf>. For now, model -# this messy process as a transition in 1855. Shanks's 1894 transition is more -# plausible for Zurich but has not been checked. +# Round BMT to the nearest even second, 0:29:46. +# +# We can find no reliable source for Shanks's assertion that all of Switzerland +# except Geneva switched to Bern Mean Time at 00:00 on 1848-09-12. This book: +# +# Jakob Messerli. Gleichmassig, punktlich, schnell: Zeiteinteilung und +# Zeitgebrauch in der Schweiz im 19. Jahrhundert. Chronos, Zurich 1995, +# ISBN 3-905311-68-2, OCLC 717570797. +# +# suggests that the transition was more gradual, and that the Swiss did not +# agree about civil time during the transition. The timekeeping it gives the +# most detail for is postal and telegraph time: here, federal legislation (the +# "Bundesgesetz uber die Erstellung von elektrischen Telegraphen") passed on +# 1851-11-23, and an official implementation notice was published 1853-07-16 +# (Bundesblatt 1853, Bd. II, S. 859). On p 72 Messerli writes that in +# practice since July 1853 Bernese time was used in "all postal and telegraph +# offices in Switzerland from Geneva to St. Gallen and Basel to Chiasso" +# (Google translation). For now, model this transition as occuring on +# 1853-07-16, though it probably occurred at some other date in Zurich, and +# legal civil time probably changed at still some other transition date. # Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S Rule Swiss 1941 1942 - May Mon>=1 1:00 1:00 S Rule Swiss 1941 1942 - Oct Mon>=1 2:00 0 - # Zone NAME GMTOFF RULES FORMAT [UNTIL] -Zone Europe/Zurich 0:34:08 - LMT 1855 # See above comment. +Zone Europe/Zurich 0:34:08 - LMT 1853 Jul 16 # See above comment. 0:29:46 - BMT 1894 Jun # Bern Mean Time 1:00 Swiss CE%sT 1981 1:00 EU CE%sT diff --git a/zic.8 b/zic.8 index a2374a1..7ea94c5 100644 --- a/zic.8 +++ b/zic.8 @@ -468,7 +468,7 @@ Rule EU 1996 max - Oct lastSun 1:00u 0 - .sp .ta \w'# Zone\0\0'u +\w'Europe/Zurich\0\0'u +\w'GMTOFF\0\0'u +\w'RULES/SAVE\0\0'u +\w'FORMAT\0\0'u # Zone NAME GMTOFF RULES/SAVE FORMAT UNTIL -Zone Europe/Zurich 0:34:08 - LMT 1855 +Zone Europe/Zurich 0:34:08 - LMT 1853 Jul 16 0:29:46 - BMT 1894 Jun 1:00 Swiss CE%sT 1981 1:00 EU CE%sT @@ -480,9 +480,9 @@ Link Europe/Zurich Switzerland In this example, the zone is named Europe/Zurich but it has an alias as Switzerland. This example says that Zurich was 34 minutes and 8 -seconds west of UT until 1855-01-01 at 00:00, when the legal offset +seconds west of UT until 1853-07-16 at 00:00, when the legal offset was changed to 7\(de\|26\(fm\|22.50\(sd; although this works out to -0:29.45.50, the input format cannot represent fractional seconds so it +0:29:45.50, the input format cannot represent fractional seconds so it is rounded here. After 1894-06-01 at 00:00 Swiss daylight saving rules (defined with lines beginning with "Rule Swiss") apply, and the UT offset became one hour. From 1981 to the present, EU daylight saving rules have -- 1.8.1.2