Be less enthusiastic about Shanks and clarify UT vs UTC.

* 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

@@ -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
 

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

asia

@@ -6,20 +6,19 @@
 # [email protected] 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

australasia

@@ -797,19 +797,19 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 # [email protected] 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

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

europe

@@ -6,16 +6,19 @@
 # [email protected] 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).

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:
 #

southamerica

@@ -6,23 +6,23 @@
 # [email protected] 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

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 @@ <h2>The <code><abbr title="time zone">tz</abbr></code> database</h2>
 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 @@ <h2>The <code><abbr title="time zone">tz</abbr></code> database</h2>
 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 @@ <h2>The <code><abbr title="time zone">tz</abbr></code> database</h2>
 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 @@ <h2>Other <code><abbr>tz</abbr></code> compilers</h2>
 <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 &ndash; World Timezone
 Definitions for Python</a> compiles <code><abbr>tz</abbr></code> source into
@@ -336,7 +346,8 @@ <h2>Other <code><abbr>tz</abbr></code> binary file readers</h2>
 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 @@ <h2>Other time zone databases</h2>
 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 @@ <h2>Precision timekeeping</h2>
 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>