From 1c8ce71c30b2acb8453b2b43c67052a6f9db2090 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Wed, 10 Jun 2020 13:51:29 -0700 Subject: [PROPOSED] =?UTF-8?q?French=20clocks=20stopped=20for=209=E2=80=B2?= =?UTF-8?q?21=E2=80=B3=20on=201911-03-11?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit (Thanks to Michael Deckers.) * NEWS, theory.html (Accuracy of the tz database): Mention this. * europe (Europe/Paris): Model the 1911-03-11 transition as occurring at 00:09:21, not at 00:01. --- NEWS | 7 +++++++ europe | 30 +++++++++++++++++++++++++++++- theory.html | 7 +++++++ 3 files changed, 43 insertions(+), 1 deletion(-) diff --git a/NEWS b/NEWS index e3ab402..5289d4e 100644 --- a/NEWS +++ b/NEWS @@ -16,6 +16,13 @@ Unreleased, experimental changes (Thanks to Géza Nyáry.) Also, the 1890 transition to standard time was on 11-01, not 10-01 (thanks to Michael Deckers). + The 1911-03-11 French transition from +00:09:21 to +00 is now + modeled as occurring at 00:09:21, not at 00:01. Legally, clocks + stopped at 00:00 for 9 minutes, 21 seconds but this cannot be + represented in tzdb, so tzdb instead represents the common + practice of keeping an old clock running until the new clock + started up. (Thanks to Michael Deckers.) + Changes to code The undocumented and ineffective tzsetwall function has been diff --git a/europe b/europe index f0acb42..4fa7119 100644 --- a/europe +++ b/europe @@ -1326,6 +1326,34 @@ Link Europe/Helsinki Europe/Mariehamn # Françoise Gauquelin, Problèmes de l'heure résolus en astrologie, # Guy Trédaniel, Paris 1987 +# From Michael Deckers (2020-06-10): +# Le Gaulois, 1911-03-11, page 1/6, online at +# https://www.retronews.fr/societe/echo-de-presse/2018/01/29/1911-change-lheure-de-paris +# ... [ Instantly, all pressure driven clock dials halted... Nine minutes and +# twenty-one seconds later the hands resumed their circular motion. ] +# There are also precise reports about how the change was prepared in train +# stations: all the publicly visible clocks stopped at midnight railway time +# (or were covered), only the chief of service had a watch, labeled +# "Heure ancienne", that he kept running until it reached 00:04:21, when +# he announced "Heure nouvelle". See the "Le Petit Journal 1911-03-11". +# https://gallica.bnf.fr/ark:/12148/bpt6k6192911/f1.item.zoom +# +# From Paul Eggert (2020-06-10): +# French time in railway stations was legally five minutes behind civil time, +# which explains why "old time" ran to 00:04:21 instead of to 00:09:21. +# The Brooklyn Daily Eagle Almanac (1912), page 494, says: +# +# ALL CLOCKS STOPPED IN FRANCE. +# On March 10, 1911, all clocks in the Republic of France were stopped +# for 9 minutes and 21 seconds. This was in obedience to a measure +# adopted by the French Senate, which went into effect at midnight.... +# Owing to this change in time a question arose in the French press as +# to whether or not a child that was born and died within the elapsed +# time could be said to have legally lived. +# +# tzdb has no way to represent stopped clocks. As the railway practice +# was to keep a watch running on "old time" to decide when to restart +# the other clocks, model this as a transition for "old time" at 00:09:21. # # Shank & Pottenger seem to use '24:00' ambiguously; resolve it with Whitman. @@ -1395,7 +1423,7 @@ Rule France 1976 only - Sep 26 1:00 0 - # on PMT-0:09:21 until 1978-08-09, when the time base finally switched to UTC. # Zone NAME STDOFF RULES FORMAT [UNTIL] Zone Europe/Paris 0:09:21 - LMT 1891 Mar 15 0:01 - 0:09:21 - PMT 1911 Mar 11 0:01 # Paris MT + 0:09:21 - PMT 1911 Mar 11 0:09:21 # Paris MT # Shanks & Pottenger give 1940 Jun 14 0:00; go with Excoffier and Le Corre. 0:00 France WE%sT 1940 Jun 14 23:00 # Le Corre says Paris stuck with occupied-France time after the liberation; diff --git a/theory.html b/theory.html index ffa3b4d..de105f2 100644 --- a/theory.html +++ b/theory.html @@ -690,6 +690,13 @@ href="https://www.dissentmagazine.org/blog/booked-a-global-history-of-time-vanes often not specified to the accuracy that the tz database requires. +
  • + The tz database cannot represent stopped clocks. + However, on 1911-03-11 at 00:00, French clocks were changed by + stopping them for 9 minutes, 21 seconds. This is approximated + in tz as a transition from 00:09:21 back + to 00:00:00 that day. +
  • Sometimes historical timekeeping was specified more precisely than what the tz code can handle. -- 2.17.1