[tz] uniform time in Switzerland in second half of 19th century

[Paul Eggert]

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 at 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