[tz] [PROPOSED PATCH 2/4] Be less enthusiastic about Shanks and clarify UT vs UTC.
Paul Eggert
eggert at cs.ucla.edu
Sat Nov 1 06:37:16 UTC 2014
* africa, asia, australasia, backzone, europe, northamerica:
* southamerica, tz-link.htm: Be less enthusiastic about Shanks.
* tz-link.htm: Be clearer about UT vs UTC.
* NEWS: Document this.
---
NEWS | 5 +++++
africa | 9 ++++-----
asia | 11 +++++------
australasia | 12 ++++++------
backzone | 5 ++---
europe | 9 ++++++---
northamerica | 12 ++++++------
southamerica | 18 +++++++++---------
tz-link.htm | 37 +++++++++++++++++++++++++------------
9 files changed, 68 insertions(+), 50 deletions(-)
diff --git a/NEWS b/NEWS
index 2485c93..deb1186 100644
--- a/NEWS
+++ b/NEWS
@@ -10,6 +10,11 @@ Unreleased, experimental changes
longer guess that Pyongyang mimicked Seoul time after World War II,
as this is politically implausible.
+ Changes affecting commentary
+
+ The commentary is less enthusiastic about Shanks as a source,
+ and is more careful to distinguish UT from UTC.
+
Release 2014i - 2014-10-21 22:04:57 -0700
diff --git a/africa b/africa
index b17c62b..1a3a176 100644
--- a/africa
+++ b/africa
@@ -8,18 +8,17 @@
# From Paul Eggert (2013-02-21):
#
-# A good source for time zone historical data outside the U.S. is
+# Unless otherwise specified, the source for data through 1990 is:
# Thomas G. Shanks and Rique Pottenger, The International Atlas (6th edition),
# San Diego: ACS Publications, Inc. (2003).
+# Unfortunately this book contains many errors and cites no sources.
#
# Gwillim Law writes that a good source
# for recent time zone data is the International Air Transport
# Association's Standard Schedules Information Manual (IATA SSIM),
# published semiannually. Law sent in several helpful summaries
-# of the IATA's data after 1990.
-#
-# Except where otherwise noted, Shanks & Pottenger is the source for
-# entries through 1990, and IATA SSIM is the source for entries afterwards.
+# of the IATA's data after 1990. Except where otherwise noted,
+# IATA SSIM is the source for entries after 1990.
#
# Another source occasionally used is Edward W. Whitman, World Time Differences,
# Whitman Publishing Co, 2 Niagara Av, Ealing, London (undated), which
diff --git a/asia b/asia
index 10262f6..1a2bd12 100644
--- a/asia
+++ b/asia
@@ -6,20 +6,19 @@
# tz at iana.org for general use in the future). For more, please see
# the file CONTRIBUTING in the tz distribution.
-# From Paul Eggert (2013-08-11):
+# From Paul Eggert (2014-10-31):
#
-# A good source for time zone historical data outside the U.S. is
+# Unless otherwise specified, the source for data through 1990 is:
# Thomas G. Shanks and Rique Pottenger, The International Atlas (6th edition),
# San Diego: ACS Publications, Inc. (2003).
+# Unfortunately this book contains many errors and cites no sources.
#
# Gwillim Law writes that a good source
# for recent time zone data is the International Air Transport
# Association's Standard Schedules Information Manual (IATA SSIM),
# published semiannually. Law sent in several helpful summaries
-# of the IATA's data after 1990.
-#
-# Except where otherwise noted, Shanks & Pottenger is the source for
-# entries through 1990, and IATA SSIM is the source for entries afterwards.
+# of the IATA's data after 1990. Except where otherwise noted,
+# IATA SSIM is the source for entries after 1990.
#
# Another source occasionally used is Edward W. Whitman, World Time Differences,
# Whitman Publishing Co, 2 Niagara Av, Ealing, London (undated), which
diff --git a/australasia b/australasia
index 8efe56f..911e681 100644
--- a/australasia
+++ b/australasia
@@ -797,19 +797,19 @@ Zone Pacific/Wallis 12:15:20 - LMT 1901
# tz at iana.org for general use in the future). For more, please see
# the file CONTRIBUTING in the tz distribution.
-# From Paul Eggert (2013-02-21):
-# A good source for time zone historical data outside the U.S. is
+# From Paul Eggert (2014-10-31):
+#
+# Unless otherwise specified, the source for data through 1990 is:
# Thomas G. Shanks and Rique Pottenger, The International Atlas (6th edition),
# San Diego: ACS Publications, Inc. (2003).
+# Unfortunately this book contains many errors and cites no sources.
#
# Gwillim Law writes that a good source
# for recent time zone data is the International Air Transport
# Association's Standard Schedules Information Manual (IATA SSIM),
# published semiannually. Law sent in several helpful summaries
-# of the IATA's data after 1990.
-#
-# Except where otherwise noted, Shanks & Pottenger is the source for
-# entries through 1990, and IATA SSIM is the source for entries afterwards.
+# of the IATA's data after 1990. Except where otherwise noted,
+# IATA SSIM is the source for entries after 1990.
#
# Another source occasionally used is Edward W. Whitman, World Time Differences,
# Whitman Publishing Co, 2 Niagara Av, Ealing, London (undated), which
diff --git a/backzone b/backzone
index 29320aa..16a998c 100644
--- a/backzone
+++ b/backzone
@@ -24,11 +24,10 @@
# replaced by links as their data entries were questionable and/or they
# differed from other zones only in pre-1970 time stamps.
-# Unless otherwise specified, the source for the data is the following,
-# which does not itself cite sources and is often wrong:
-#
+# Unless otherwise specified, the source for data through 1990 is:
# Thomas G. Shanks and Rique Pottenger, The International Atlas (6th edition),
# San Diego: ACS Publications, Inc. (2003).
+# Unfortunately this book contains many errors and cites no sources.
# This file is not intended to be compiled standalone, as it
# assumes rules from other files. In the tz distribution, use
diff --git a/europe b/europe
index 27a8b30..be93bb4 100644
--- a/europe
+++ b/europe
@@ -6,16 +6,19 @@
# tz at iana.org for general use in the future). For more, please see
# the file CONTRIBUTING in the tz distribution.
-# From Paul Eggert (2014-05-31):
-# A good source for time zone historical data outside the U.S. is
+# From Paul Eggert (2014-10-31):
+#
+# Unless otherwise specified, the source for data through 1990 is:
# Thomas G. Shanks and Rique Pottenger, The International Atlas (6th edition),
# San Diego: ACS Publications, Inc. (2003).
+# Unfortunately this book contains many errors and cites no sources.
#
# Gwillim Law writes that a good source
# for recent time zone data is the International Air Transport
# Association's Standard Schedules Information Manual (IATA SSIM),
# published semiannually. Law sent in several helpful summaries
-# of the IATA's data after 1990.
+# of the IATA's data after 1990. Except where otherwise noted,
+# IATA SSIM is the source for entries after 1990.
#
# A reliable and entertaining source about time zones is
# Derek Howse, Greenwich time and longitude, Philip Wilson Publishers (1997).
diff --git a/northamerica b/northamerica
index 07f527f..87bd032 100644
--- a/northamerica
+++ b/northamerica
@@ -991,19 +991,19 @@ Zone America/Menominee -5:50:27 - LMT 1885 Sep 18 12:00
################################################################################
-# From Paul Eggert (2006-03-22):
-# A good source for time zone historical data outside the U.S. is
+# From Paul Eggert (2014-10-31):
+#
+# Unless otherwise specified, the source for data through 1990 is:
# Thomas G. Shanks and Rique Pottenger, The International Atlas (6th edition),
# San Diego: ACS Publications, Inc. (2003).
+# Unfortunately this book contains many errors and cites no sources.
#
# Gwillim Law writes that a good source
# for recent time zone data is the International Air Transport
# Association's Standard Schedules Information Manual (IATA SSIM),
# published semiannually. Law sent in several helpful summaries
-# of the IATA's data after 1990.
-#
-# Except where otherwise noted, Shanks & Pottenger is the source for
-# entries through 1990, and IATA SSIM is the source for entries afterwards.
+# of the IATA's data after 1990. Except where otherwise noted,
+# IATA SSIM is the source for entries after 1990.
#
# Other sources occasionally used include:
#
diff --git a/southamerica b/southamerica
index e246646..bdc29c2 100644
--- a/southamerica
+++ b/southamerica
@@ -6,23 +6,23 @@
# tz at iana.org for general use in the future). For more, please see
# the file CONTRIBUTING in the tz distribution.
-# From Paul Eggert (2006-03-22):
-# A good source for time zone historical data outside the U.S. is
+# From Paul Eggert (2014-10-31):
+#
+# Unless otherwise specified, the source for data through 1990 is:
# Thomas G. Shanks and Rique Pottenger, The International Atlas (6th edition),
# San Diego: ACS Publications, Inc. (2003).
-#
-# For data circa 1899, a common source is:
-# Milne J. Civil time. Geogr J. 1899 Feb;13(2):173-94.
-# http://www.jstor.org/stable/1774359
+# Unfortunately this book contains many errors and cites no sources.
#
# Gwillim Law writes that a good source
# for recent time zone data is the International Air Transport
# Association's Standard Schedules Information Manual (IATA SSIM),
# published semiannually. Law sent in several helpful summaries
-# of the IATA's data after 1990.
+# of the IATA's data after 1990. Except where otherwise noted,
+# IATA SSIM is the source for entries after 1990.
#
-# Except where otherwise noted, Shanks & Pottenger is the source for
-# entries through 1990, and IATA SSIM is the source for entries afterwards.
+# For data circa 1899, a common source is:
+# Milne J. Civil time. Geogr J. 1899 Feb;13(2):173-94.
+# http://www.jstor.org/stable/1774359
#
# Earlier editions of these tables used the North American style (e.g. ARST and
# ARDT for Argentine Standard and Daylight Time), but the following quote
diff --git a/tz-link.htm b/tz-link.htm
index 98594f4..0dbd1b0 100644
--- a/tz-link.htm
+++ b/tz-link.htm
@@ -8,7 +8,7 @@
<meta http-equiv="Content-type" content='text/html; charset="UTF-8"'>
<meta name="DC.Creator" content="Eggert, Paul">
<meta name="DC.Contributor" content="Olson, Arthur David">
-<meta name="DC.Date" content="2014-10-21">
+<meta name="DC.Date" content="2014-10-31">
<meta name="DC.Description"
content="Sources of information about time zones and daylight saving time">
<meta name="DC.Identifier"
@@ -26,9 +26,7 @@ that represent the history of local time
for many representative locations around the globe.
It is updated periodically to reflect changes made by political bodies
to <a href="http://en.wikipedia.org/wiki/Time_zone">time zone</a>
-boundaries, <a
-href="http://en.wikipedia.org/wiki/Coordinated_Universal_Time"><abbr
-title="Coordinated Universal Time">UTC</abbr></a> offsets, and
+boundaries and
<a href="http://en.wikipedia.org/wiki/Daylight_saving">daylight-saving</a>
rules.
This database (often called <code>zoneinfo</code> or
@@ -65,7 +63,7 @@ title="Virtual Memory System">VMS</abbr></a>,
X</abbr></a>, and
<a href="http://oracle.com/solaris">Solaris</a>.</p>
<p>
-Each location in the database represents a national region where all
+Each location in the database represents a region where all
clocks keeping local time have agreed since 1970.
Locations are identified by continent or ocean and then by the name of
the location, which is typically the largest city within the region.
@@ -86,6 +84,18 @@ implementation set the <code><abbr>TZ</abbr></code>
environment variable to the location's full name,
e.g., <code><abbr>TZ</abbr>="America/New_York"</code>.</p>
<p>
+Associated with each region is a history of offsets from
+<a href="http://en.wikipedia.org/wiki/Universal_Time">Universal
+Time</a> (<abbr>UT</abbr>), which is <a
+href="http://en.wikipedia.org/wiki/Greenwich_Mean_Time">Greenwich Mean
+Time</a> (<abbr>GMT</abbr>) with days beginning at midnight;
+for time stamps after 1960 this is more precisely <a
+href="http://en.wikipedia.org/wiki/Coordinated_Universal_Time">Coordinated
+Universal Time</a> (<abbr>UTC</abbr>).
+The database also records when daylight saving time was in use,
+along with alphabetic time zone abbreviations such as <abbr>EST</abbr>
+for Eastern Standard Time in the <abbr>US</abbr>.</p>
+<p>
In the <code><abbr>tz</abbr></code> database's
<a href="ftp://ftp.iana.org/tz/releases/"><abbr
title="File Transfer Protocol">FTP</abbr> releases</a>
@@ -297,8 +307,8 @@ license.</li>
<abbr>API</abbr> is upward compatible with standard JavaScript
Dates. It is freely available under the Apache License.</li>
<li><a href="https://github.com/sproutsocial/walltime-js">Walltime-js</a>
-translates UTC to local time. It is freely available under the <abbr>MIT</abbr>
-license.</li>
+translates <abbr>UT</abbr> to local time. It is freely available under
+the <abbr>MIT</abbr> license.</li>
</ul>
<li><a href="http://pytz.sourceforge.net">pytz – World Timezone
Definitions for Python</a> compiles <code><abbr>tz</abbr></code> source into
@@ -336,7 +346,8 @@ This library is freely available under the
and is widely used in <abbr>GNU</abbr>/Linux systems.</li>
<li><a href="http://www.gnome.org/">GNOME</a>'s Glib has
a <code><abbr>tz</abbr></code> binary file reader written in C that
-creates a <code>GTimeZone</code> object representing sets of UTC offsets.
+creates a <code>GTimeZone</code> object representing sets
+of <abbr>UT</abbr> offsets.
It is freely available under the <abbr>LGPL</abbr>.</li>
<li><a href="http://bmsi.com/java/#TZ">ZoneInfo.java</a>
is a <code><abbr>tz</abbr></code> binary file reader written in Java.
@@ -432,7 +443,10 @@ href="http://www.astrocom.com/astrology/books/american-atlas">one volume
for the <abbr>US</abbr></a>, and <a
href="http://www.astrocom.com/astrology/books/international-atlas">one for
other locations</a>) by <a
-href="http://astrocom.com/">Astro Computing Services</a>.</li>
+href="http://astrocom.com/">Astro Computing Services</a>.
+These atlases are extensive but unreliable, as Shanks appears to have
+guessed many <abbr>UT</abbr> offsets and transitions. The atlases cite no
+sources and do not indicate which entries are guesswork.</li>
<li><a href="http://www.hp.com/go/hpux/">HP-UX</a> has a database in
its own <code>tztab</code>(4) format.</li>
<li>Microsoft Windows has proprietary data mentioned above.</li>
@@ -626,9 +640,8 @@ specifies a <a
href="http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol"><abbr>DHCP</abbr></a>
option for a server to configure
a client's time zone and daylight saving settings automatically.</li>
-<li><a href="http://gauss.gge.unb.ca/GMT.UT.and.the.RGO.html">A Few
-Facts Concerning <abbr title="Greenwich Mean Time">GMT</abbr>, <abbr
-title="Universal Time">UT</abbr>, and
+<li><a href="http://gauss.gge.unb.ca/GMT.UT.and.the.RGO.html">A Few Facts
+Concerning <abbr>GMT</abbr>, <abbr>UT</abbr>, and
the <abbr title="Royal Greenwich Observatory">RGO</abbr></a>
answers questions like "What is the
difference between <abbr>GMT</abbr> and <abbr>UTC</abbr>?"</li>
--
1.9.1
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