IANA 2018g

13 files changed, 368 insertions, 128 deletions

diff --git a/tz/NEWS b/tz/NEWS
index aeeef10..d4cb723 100644
--- a/tz/NEWS
+++ b/tz/NEWS
@@ -1,5 +1,40 @@
 News for the tz database
 
+Release 2018g - 2018-10-26 22:22:45 -0700
+
+  Briefly:
+    Morocco switches to permanent +01 on 2018-10-27.
+
+  Changes to future timestamps
+
+    Morocco switches from +00/+01 to permanent +01 effective 2018-10-27,
+    so its clocks will not fall back on 2018-10-28 as previously scheduled.
+    (Thanks to Mohamed Essedik Najd and Brian Inglis.)
+
+  Changes to code
+
+    When generating TZif files with leap seconds, zic no longer uses a
+    format that trips up older 32-bit clients, fixing a bug introduced
+    in 2018f.  (Reported by Daniel Fischer.)  Also, the zic workaround
+    for QTBUG-53071 now also works for TZif files with leap seconds.
+
+    The translator to rearguard format now rewrites the line
+    "Rule Japan 1948 1951 - Sep Sat>=8 25:00 0 S" to
+    "Rule Japan 1948 1951 - Sep Sun>=9  1:00 0 S".
+    This caters to zic before 2007 and to Oracle TZUpdater 2.2.0
+    and earlier.  (Reported by Christos Zoulas.)
+
+  Changes to past time zone abbreviations
+
+    Change HDT to HWT/HPT for WWII-era abbreviations in Hawaii.
+    This reverts to 2011h, as the abbreviation change in 2011i was
+    likely inadvertent.
+
+  Changes to documentation
+
+    tzfile.5 has new sections on interoperability issues.
+
+
 Release 2018f - 2018-10-18 00:14:18 -0700
 
   Briefly:
diff --git a/tz/africa b/tz/africa
index 555052b..a26b91b 100644
--- a/tz/africa
+++ b/tz/africa
@@ -844,94 +844,61 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 # <https://lnt.ma/le-maroc-reculera-dune-heure-le-dimanche-14-juin/> agrees
 # with the patch.
 
-# From Paul Eggert (2015-06-08):
-# For now, guess that later spring and fall transitions will use 2015's rules,
-# and guess that Morocco will switch to standard time at 03:00 the last
-# Sunday before Ramadan, and back to DST at 02:00 the first Sunday after
-# Ramadan.  To implement this, transition dates for 2016 through 2037 were
-# determined by running the following program under GNU Emacs 24.3, with the
-# results integrated by hand into the table below.
-# (let ((islamic-year 1437))
-#   (require 'cal-islam)
-#   (while (< islamic-year 1460)
-#     (let ((a (calendar-islamic-to-absolute (list 9 1 islamic-year)))
-#           (b (calendar-islamic-to-absolute (list 10 1 islamic-year)))
-#           (sunday 0))
-#       (while (/= sunday (mod (setq a (1- a)) 7)))
-#       (while (/= sunday (mod b 7))
-#         (setq b (1+ b)))
-#       (setq a (calendar-gregorian-from-absolute a))
-#       (setq b (calendar-gregorian-from-absolute b))
-#       (insert
-#        (format
-#         (concat "Rule\tMorocco\t%d\tonly\t-\t%s\t%2d\t 3:00\t0\t-\n"
-#                 "Rule\tMorocco\t%d\tonly\t-\t%s\t%2d\t 2:00\t1:00\tS\n")
-#         (car (cdr (cdr a))) (calendar-month-name (car a) t) (car (cdr a))
-#         (car (cdr (cdr b))) (calendar-month-name (car b) t) (car (cdr b)))))
-#     (setq islamic-year (+ 1 islamic-year))))
+# From Mohamed Essedik Najd (2018-10-26):
+# Today, a Moroccan government council approved the perpetual addition
+# of 60 minutes to the regular Moroccan timezone.
+# From Brian Inglis (2018-10-26):
+# http://www.maroc.ma/fr/actualites/le-conseil-de-gouvernement-adopte-un-projet-de-decret-relatif-lheure-legale-stipulant-le
 
 # RULE	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
-
-Rule	Morocco	1939	only	-	Sep	12	 0:00	1:00	S
+Rule	Morocco	1939	only	-	Sep	12	 0:00	1:00	-
 Rule	Morocco	1939	only	-	Nov	19	 0:00	0	-
-Rule	Morocco	1940	only	-	Feb	25	 0:00	1:00	S
+Rule	Morocco	1940	only	-	Feb	25	 0:00	1:00	-
 Rule	Morocco	1945	only	-	Nov	18	 0:00	0	-
-Rule	Morocco	1950	only	-	Jun	11	 0:00	1:00	S
+Rule	Morocco	1950	only	-	Jun	11	 0:00	1:00	-
 Rule	Morocco	1950	only	-	Oct	29	 0:00	0	-
-Rule	Morocco	1967	only	-	Jun	 3	12:00	1:00	S
+Rule	Morocco	1967	only	-	Jun	 3	12:00	1:00	-
 Rule	Morocco	1967	only	-	Oct	 1	 0:00	0	-
-Rule	Morocco	1974	only	-	Jun	24	 0:00	1:00	S
+Rule	Morocco	1974	only	-	Jun	24	 0:00	1:00	-
 Rule	Morocco	1974	only	-	Sep	 1	 0:00	0	-
-Rule	Morocco	1976	1977	-	May	 1	 0:00	1:00	S
+Rule	Morocco	1976	1977	-	May	 1	 0:00	1:00	-
 Rule	Morocco	1976	only	-	Aug	 1	 0:00	0	-
 Rule	Morocco	1977	only	-	Sep	28	 0:00	0	-
-Rule	Morocco	1978	only	-	Jun	 1	 0:00	1:00	S
+Rule	Morocco	1978	only	-	Jun	 1	 0:00	1:00	-
 Rule	Morocco	1978	only	-	Aug	 4	 0:00	0	-
-Rule	Morocco	2008	only	-	Jun	 1	 0:00	1:00	S
+Rule	Morocco	2008	only	-	Jun	 1	 0:00	1:00	-
 Rule	Morocco	2008	only	-	Sep	 1	 0:00	0	-
-Rule	Morocco	2009	only	-	Jun	 1	 0:00	1:00	S
+Rule	Morocco	2009	only	-	Jun	 1	 0:00	1:00	-
 Rule	Morocco	2009	only	-	Aug	21	 0:00	0	-
-Rule	Morocco	2010	only	-	May	 2	 0:00	1:00	S
+Rule	Morocco	2010	only	-	May	 2	 0:00	1:00	-
 Rule	Morocco	2010	only	-	Aug	 8	 0:00	0	-
-Rule	Morocco	2011	only	-	Apr	 3	 0:00	1:00	S
+Rule	Morocco	2011	only	-	Apr	 3	 0:00	1:00	-
 Rule	Morocco	2011	only	-	Jul	31	 0:00	0	-
-Rule	Morocco	2012	2013	-	Apr	lastSun	 2:00	1:00	S
+Rule	Morocco	2012	2013	-	Apr	lastSun	 2:00	1:00	-
 Rule	Morocco	2012	only	-	Jul	20	 3:00	0	-
-Rule	Morocco	2012	only	-	Aug	20	 2:00	1:00	S
+Rule	Morocco	2012	only	-	Aug	20	 2:00	1:00	-
 Rule	Morocco	2012	only	-	Sep	30	 3:00	0	-
 Rule	Morocco	2013	only	-	Jul	 7	 3:00	0	-
-Rule	Morocco	2013	only	-	Aug	10	 2:00	1:00	S
-Rule	Morocco	2013	max	-	Oct	lastSun	 3:00	0	-
-Rule	Morocco	2014	2021	-	Mar	lastSun	 2:00	1:00	S
+Rule	Morocco	2013	only	-	Aug	10	 2:00	1:00	-
+Rule	Morocco	2013	2018	-	Oct	lastSun	 3:00	0	-
+Rule	Morocco	2014	2018	-	Mar	lastSun	 2:00	1:00	-
 Rule	Morocco	2014	only	-	Jun	28	 3:00	0	-
-Rule	Morocco	2014	only	-	Aug	 2	 2:00	1:00	S
+Rule	Morocco	2014	only	-	Aug	 2	 2:00	1:00	-
 Rule	Morocco	2015	only	-	Jun	14	 3:00	0	-
-Rule	Morocco	2015	only	-	Jul	19	 2:00	1:00	S
+Rule	Morocco	2015	only	-	Jul	19	 2:00	1:00	-
 Rule	Morocco	2016	only	-	Jun	 5	 3:00	0	-
-Rule	Morocco	2016	only	-	Jul	10	 2:00	1:00	S
+Rule	Morocco	2016	only	-	Jul	10	 2:00	1:00	-
 Rule	Morocco	2017	only	-	May	21	 3:00	0	-
-Rule	Morocco	2017	only	-	Jul	 2	 2:00	1:00	S
+Rule	Morocco	2017	only	-	Jul	 2	 2:00	1:00	-
 Rule	Morocco	2018	only	-	May	13	 3:00	0	-
-Rule	Morocco	2018	only	-	Jun	17	 2:00	1:00	S
-Rule	Morocco	2019	only	-	May	 5	 3:00	0	-
-Rule	Morocco	2019	only	-	Jun	 9	 2:00	1:00	S
-Rule	Morocco	2020	only	-	Apr	19	 3:00	0	-
-Rule	Morocco	2020	only	-	May	24	 2:00	1:00	S
-Rule	Morocco	2021	only	-	Apr	11	 3:00	0	-
-Rule	Morocco	2021	only	-	May	16	 2:00	1:00	S
-Rule	Morocco	2022	only	-	May	 8	 2:00	1:00	S
-Rule	Morocco	2023	only	-	Apr	23	 2:00	1:00	S
-Rule	Morocco	2024	only	-	Apr	14	 2:00	1:00	S
-Rule	Morocco	2025	only	-	Apr	 6	 2:00	1:00	S
-Rule	Morocco	2026	max	-	Mar	lastSun	 2:00	1:00	S
-Rule	Morocco	2036	only	-	Oct	19	 3:00	0	-
-Rule	Morocco	2037	only	-	Oct	 4	 3:00	0	-
+Rule	Morocco	2018	only	-	Jun	17	 2:00	1:00	-
 
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone Africa/Casablanca	-0:30:20 -	LMT	1913 Oct 26
-			 0:00	Morocco	WE%sT	1984 Mar 16
-			 1:00	-	CET	1986
-			 0:00	Morocco	WE%sT
+			 0:00	Morocco	+00/+01	1984 Mar 16
+			 1:00	-	+01	1986
+			 0:00	Morocco	+00/+01	2018 Oct 27
+			 1:00	-	+01
 
 # Western Sahara
 #
@@ -946,7 +913,8 @@ Zone Africa/Casablanca	-0:30:20 -	LMT	1913 Oct 26
 
 Zone Africa/El_Aaiun	-0:52:48 -	LMT	1934 Jan # El Aaiún
 			-1:00	-	-01	1976 Apr 14
-			 0:00	Morocco	WE%sT
+			 0:00	Morocco	+00/+01	2018 Oct 27
+			 1:00	-	+01
 
 # Mozambique
 #
diff --git a/tz/europe b/tz/europe
index 5b0a829..587f7b0 100644
--- a/tz/europe
+++ b/tz/europe
@@ -3440,7 +3440,8 @@ Rule	Spain	1978	only	-	Oct	 1	 2:00s	0	-
 #Rule NatSpain	1937	only	-	May	22	23:00	1:00	S
 #Rule NatSpain	1937	1938	-	Oct	Sat>=1	24:00s	0	-
 #Rule NatSpain	1938	only	-	Mar	26	23:00	1:00	S
-# The following rules are copied from Morocco from 1967 through 1978.
+# The following rules are copied from Morocco from 1967 through 1978,
+# except with "S" letters.
 Rule SpainAfrica 1967	only	-	Jun	 3	12:00	1:00	S
 Rule SpainAfrica 1967	only	-	Oct	 1	 0:00	0	-
 Rule SpainAfrica 1974	only	-	Jun	24	 0:00	1:00	S
diff --git a/tz/northamerica b/tz/northamerica
index 88c0f6f..9d5bad2 100644
--- a/tz/northamerica
+++ b/tz/northamerica
@@ -439,6 +439,19 @@ Zone America/North_Dakota/Beulah -6:47:07 - LMT	1883 Nov 18 12:12:53
 # western South Dakota, far western Texas (El Paso County, Hudspeth County,
 # and Pine Springs and Nickel Creek in Culberson County), Utah, Wyoming
 #
+# From Paul Eggert (2018-10-25):
+# On 1921-03-04 federal law placed all of Texas into the central time zone.
+# However, El Paso ignored the law for decades and continued to observe
+# mountain time, on the grounds that that's what they had always done
+# and they weren't about to let the federal government tell them what to do.
+# Eventually the federal government gave in and changed the law on
+# 1970-04-10 to match what El Paso was actually doing.  Although
+# that's slightly after our 1970 cutoff, there is no need to create a
+# separate zone for El Paso since they were ignoring the law anyway.  See:
+# Long T. El Pasoans were time rebels, fought to stay in Mountain zone.
+# El Paso Times. 2018-10-24 06:40 -06.
+# https://www.elpasotimes.com/story/news/local/el-paso/2018/10/24/el-pasoans-were-time-rebels-fought-stay-mountain-zone/1744509002/
+#
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER
 Rule	Denver	1920	1921	-	Mar	lastSun	2:00	1:00	D
 Rule	Denver	1920	only	-	Oct	lastSun	2:00	0	S
@@ -708,9 +721,7 @@ Zone America/Adak	 12:13:22 -	LMT	1867 Oct 19 12:44:35
 Zone Pacific/Honolulu	-10:31:26 -	LMT	1896 Jan 13 12:00
 			-10:30	-	HST	1933 Apr 30  2:00
 			-10:30	1:00	HDT	1933 May 21 12:00
-			-10:30	-	HST	1942 Feb  9  2:00
-			-10:30	1:00	HDT	1945 Sep 30  2:00
-			-10:30	-	HST	1947 Jun  8  2:00
+			-10:30	US	H%sT	1947 Jun  8  2:00
 			-10:00	-	HST
 
 # Now we turn to US areas that have diverged from the consensus since 1970.
diff --git a/tz/theory.html b/tz/theory.html
index 8dd58db..e9c9716 100644
--- a/tz/theory.html
+++ b/tz/theory.html
@@ -407,7 +407,7 @@ in decreasing order of importance:
       EST/EDT/EWT/EPT/EDDT Eastern [North America],
       EET/EEST Eastern European,
       GST Guam,
-      HST/HDT Hawaii,
+      HST/HDT/HWT/HPT Hawaii,
       HKT/HKST Hong Kong,
       IST India,
       IST/GMT Irish,
diff --git a/tz/tz-how-to.html b/tz/tz-how-to.html
index 159ed89..8471b67 100644
--- a/tz/tz-how-to.html
+++ b/tz/tz-how-to.html
@@ -459,8 +459,8 @@ given alphabetic string.</li>
 <p>An example of a specific amount of time is:</p>
 <pre>
 #Zone NAME            GMTOFF RULES FORMAT [UNTIL]
-Zone Pacific/Honolulu ...                 1933 Apr 30 2:00
-                      -10:30 1:00  HDT    1933 May 21 2:00
+Zone Pacific/Honolulu ...                 1933 Apr 30  2:00
+                      -10:30 1:00  HDT    1933 May 21 12:00
                       ...
 </pre>
 
@@ -559,7 +559,7 @@ the true offset is undefined.
 Rule  US   1918 1919 -    Oct lastSun  2:00  0    S
 Rule  US   1942 only -    Feb  9       2:00  1:00 W # War
 Rule  US   1945 only -    Aug 14      23:00u 1:00 P # Peace
-Rule  US   1945 only -    Sep 30       2:00  0    S
+Rule  US   1945 only -    Sep lastSun  2:00  0    S
 </pre>
   </td></tr></table></td>
 </tr>
@@ -570,7 +570,7 @@ Rule  US   1945 only -    Sep 30       2:00  0    S
   <td colspan="6" align="center"><table><tr><td>
 <pre>
 #Zone NAME            GMTOFF    RULES FORMAT [UNTIL]
-Zone Pacific/Honolulu -10:31:26 -     LMT    1900 Jan  1 12:00
+Zone Pacific/Honolulu -10:31:26 -     LMT    1896 Jan 13 12:00
                       -10:30    -     HST    1933 Apr 30  2:00
                       -10:30    1:00  HDT    1933 May 21  2:00
                       -10:30    US    H%sT   1947 Jun  8  2:00
@@ -598,7 +598,7 @@ Zone Pacific/Honolulu -10:31:26 -     LMT    1900 Jan  1 12:00
   <td>&mdash;</td>
   <td>LMT</td>
   <td>local mean time</td>
-  <td>1900-01-01</td>
+  <td>1896-01-13</td>
   <td>12:00</td>
 </tr>
 <tr align="center">
@@ -607,7 +607,7 @@ Zone Pacific/Honolulu -10:31:26 -     LMT    1900 Jan  1 12:00
   <td>HST</td>
   <td>Hawaii standard time</td>
   <td>1933-04-30</td>
-  <td rowspan="3">02:00</td>
+  <td>02:00</td>
 </tr>
 <tr align="center">
   <td>&minus;9:30</td>
@@ -615,6 +615,7 @@ Zone Pacific/Honolulu -10:31:26 -     LMT    1900 Jan  1 12:00
   <td>HDT</td>
   <td>Hawaii daylight time</td>
   <td>1933-05-21</td>
+  <td>12:00</td>
 </tr>
 <tr align="center">
   <td>&minus;10:30&sup1;</td>
@@ -622,6 +623,7 @@ Zone Pacific/Honolulu -10:31:26 -     LMT    1900 Jan  1 12:00
   <td>HST&sup1;</td>
   <td>Hawaii standard time</td>
   <td>1942-02-09</td>
+  <td>02:00</td>
 </tr>
 <tr align="center">
   <td rowspan="2">&minus;9:30</td>
diff --git a/tz/tz-link.html b/tz/tz-link.html
index 8593ba6..956af52 100644
--- a/tz/tz-link.html
+++ b/tz/tz-link.html
@@ -524,10 +524,11 @@ clock (intclock)</a> is a clock that displays multiple time zones on
 under the <abbr>GPL</abbr>.</li>
 <li>Microsoft Windows 8.1
 and later has <code><abbr>tz</abbr></code> data and <abbr>CLDR</abbr>
-data (mentioned <a href="#CLDR">below</a>) used by
-<a href="https://en.wikipedia.org/wiki/Windows_Runtime">Windows Runtime</a>
-classes such as <a
-href="https://msdn.microsoft.com/en-us/library/windows/apps/windows.globalization.datetimeformatting.datetimeformatter.aspx"><code>DateTimeFormatter</code></a>.
+data (mentioned <a href="#CLDR">below</a>) used by the
+<a href="https://en.wikipedia.org/wiki/Windows_Runtime">Windows Runtime</a> /
+<a href="https://en.wikipedia.org/wiki/Universal_Windows_Platform">Universal Windows Platform</a> classes
+<a href="https://docs.microsoft.com/uwp/api/Windows.Globalization.DateTimeFormatting.DateTimeFormatter"><code>DateTimeFormatter</code></a> and
+<a href="https://docs.microsoft.com/uwp/api/windows.globalization.calendar"><code>Calendar</code></a>.
 <a id="System.TimeZoneInfo"
 href="https://blogs.msdn.microsoft.com/bclteam/2007/06/07/exploring-windows-time-zones-with-system-timezoneinfo-josh-free/">Exploring
 Windows Time Zones with <code>System.TimeZoneInfo</code></a> describes
@@ -540,6 +541,8 @@ Tzid table</a> or <a
 href="https://unicode.org/repos/cldr/trunk/common/supplemental/windowsZones.xml"><abbr>XML</abbr>
 file</a> of the <abbr>CLDR</abbr> data maps proprietary zone IDs
 to <code><abbr>tz</abbr></code> names.
+These mappings can be performed programmatically via the <a href="https://github.com/mj1856/TimeZoneConverter">TimeZoneConverter</a> .NET library,
+or the ICU Java and C++ libraries mentioned <a href="#ICU">above</a>.
 <li><a
 href="https://www.oracle.com/java/index.html">Oracle
 Java</a> contains a copy of a subset of a recent
@@ -742,6 +745,14 @@ zones &amp; daylight saving time</a>.</dd>
 <dd>The Hydrographic and Oceanographic Service of the Chilean Navy publishes a
 <a href="http://www.horaoficial.cl/historia_hora.html" hreflang="es">history of
 Chile's official time (in Spanish)</a>.</dd>
+<dt>China</dt>
+<dd>The Hong Kong Observatory maintains a
+<a href="https://www.hko.gov.hk/gts/time/Summertime.htm">history of
+ summer time in Hong Kong</a>,
+and Macau's Meteorological and Geophysical Bureau maintains a <a
+href="http://www.smg.gov.mo/smg/geophysics/e_t_Summer%20Time.htm">similar
+history for Macau</a>.
+Unfortunately the latter is incomplete and has errors.</dd>
 <dt>Czech Republic</dt>
 <dd><a href="https://kalendar.beda.cz/kdy-zacina-a-konci-letni-cas"
 hreflang="cs">When daylight saving time starts and ends (in Czech)</a>
@@ -758,10 +769,6 @@ hreflang="he">announcements (in Hebrew)</a>.</dd>
 <dd>The National Institute of Metrological Research maintains a
 <a href="http://oldsite.inrim.it/res/tf/ora_legale_i.shtml">table of civil time
 (in Italian)</a>.</dd>
-<dt>Macau</dt>
-<dd>The Meteorological and Geophysical Bureau maintains a
-<a href="http://www.smg.gov.mo/smg/geophysics/e_t_Summer%20Time.htm">history
-of summer time</a>. Unfortunately it is incomplete and has errors.</dd>
 <dt>Malaysia</dt>
 <dd>See Singapore <a href="#Singapore">below</a>.</dd>
 <dt>Mexico</dt>
diff --git a/tz/tzfile.5 b/tz/tzfile.5
index 79b19bf..bbdccfc 100644
--- a/tz/tzfile.5
+++ b/tz/tzfile.5
@@ -9,6 +9,8 @@ tzfile \- timezone information
 .de q
 \\$3\*(lq\\$1\*(rq\\$2
 ..
+.ie \n(.g .ds - \f(CW-\fP
+.el ds - \-
 The timezone information files used by
 .BR tzset (3)
 are typically found under a directory with a name like
@@ -186,8 +188,196 @@ from 0 through 24.
 Second, DST is in effect all year if it starts
 January 1 at 00:00 and ends December 31 at 24:00 plus the difference
 between daylight saving and standard time.
-.PP
+.SS Interoperability considerations
 Future changes to the format may append more data.
+.PP
+Version 1 files are considered a legacy format and
+should be avoided, as they do not support transition
+times after the year 2038.
+Readers that only understand Version 1 must ignore
+any data that extends beyond the calculated end of the version
+1 data block.
+.PP
+Writers should generate a version 3 file if
+TZ string extensions are necessary to accurately
+model transition times.
+Otherwise, version 2 files should be generated.
+.PP
+The sequence of time changes defined by the version 1
+header and data block should be a contiguous subsequence
+of the time changes defined by the version 2+ header and data
+block, and by the footer.
+This guideline helps obsolescent version 1 readers
+agree with current readers about timestamps within the
+contiguous subsequence.  It also lets writers not
+supporting obsolescent readers use a
+.I tzh_timecnt
+of zero
+in the version 1 data block to save space.
+.PP
+Time zone designations should consist of at least three (3)
+and no more than six (6) ASCII characters from the set of
+alphanumerics,
+.q "-",
+and
+.q "+".
+This is for compatibility with POSIX requirements for
+time zone abbreviations.
+.PP
+When reading a version 2 or 3 file, readers
+should ignore the version 1 header and data block except for
+the purpose of skipping over them.
+.PP
+Readers should calculate the total lengths of the
+headers and data blocks and check that they all fit within
+the actual file size, as part of a validity check for the file.
+.SS Common interoperability issues
+This section documents common problems in reading or writing TZif files.
+Most of these are problems in generating TZif files for use by
+older readers.
+The goals of this section are:
+.IP * 2
+to help TZif writers output files that avoid common
+pitfalls in older or buggy TZif readers,
+.IP *
+to help TZif readers avoid common pitfalls when reading
+files generated by future TZif writers, and
+.IP *
+to help any future specification authors see what sort of
+problems arise when the TZif format is changed.
+.PP
+When new versions of the TZif format have been defined, a
+design goal has been that a reader can successfully use a TZif
+file even if the file is of a later TZif version than what the
+reader was designed for.
+When complete compatibility was not achieved, an attempt was
+made to limit glitches to rarely-used timestamps, and to allow
+simple partial workarounds in writers designed to generate
+new-version data useful even for older-version readers.
+This section attempts to document these compatibility issues and
+workarounds, as well as to document other common bugs in
+readers.
+.PP
+Interoperability problems with TZif include the following:
+.IP * 2
+Some readers examine only version 1 data.
+As a partial workaround, a writer can output as much version 1
+data as possible.
+However, a reader should ignore version 1 data, and should use
+version 2+ data even if the reader's native timestamps have only
+32 bits.
+.IP *
+Some readers designed for version 2 might mishandle
+timestamps after a version 3 file's last transition, because
+they cannot parse extensions to POSIX in the TZ-like string.
+As a partial workaround, a writer can output more transitions
+than necessary, so that only far-future timestamps are
+mishandled by version 2 readers.
+.IP *
+Some readers designed for version 2 do not support
+permanent daylight saving time, e.g., a TZ string
+.q "EST5EDT,0/0,J365/25"
+denoting permanent Eastern Daylight Time (\*-04).
+As a partial workaround, a writer can substitute standard time
+for the next time zone east, e.g.,
+.q "AST4"
+for permanent Atlantic Standard Time (\*-04).
+.IP *
+Some readers ignore the footer, and instead predict future
+timestamps from the time type of the last transition.
+As a partial workaround, a writer can output more transitions
+than necessary.
+.IP *
+Some readers do not use time type 0 for timestamps before
+the first transition, in that they infer a time type using a
+heuristic that does not always select time type 0.
+As a partial workaround, a writer can output a dummy (no-op)
+first transition at an early time.
+.IP *
+Some readers mishandle timestamps before the first
+transition that has a timestamp not less than -2**31.
+Readers that support only 32-bit timestamps are likely to be
+more prone to this problem, for example, when they process
+64-bit transitions only some of which are representable in 32
+bits.
+As a partial workaround, a writer can output a dummy
+transition at timestamp \*-2**31.
+.IP *
+Some readers mishandle a transition if its timestamp has
+the minimum possible signed 64-bit value.
+Timestamps less than \*-2**59 are not recommended.
+.IP *
+Some readers mishandle POSIX-style TZ strings that
+contain
+.q "<"
+or
+.q ">".
+As a partial workaround, a writer can avoid using
+.q "<"
+or
+.q ">"
+for time zone abbreviations containing only alphabetic
+characters.
+.IP *
+Many readers mishandle time zone abbreviations that contain
+non-ASCII characters.
+These characters are not recommended.
+.IP *
+Some readers may mishandle time zone abbreviations that
+contain fewer than 3 or more than 6 characters, or that
+contain ASCII characters other than alphanumerics,
+.q "-",
+and
+.q "+".
+These abbreviations are not recommended.
+.IP *
+Some readers mishandle TZif files that specify
+daylight-saving time UT offsets that are less than the UT
+offsets for the corresponding standard time.
+These readers do not support locations like Ireland, which
+uses the equivalent of the POSIX TZ string
+.q "IST\*-1GMT0,M10.5.0,M3.5.0/1",
+observing standard time
+(IST, +01) in summer and daylight saving time (GMT, +00) in winter.
+As a partial workaround, a writer can output data for the
+equivalent of the POSIX TZ string
+.q "GMT0IST,M3.5.0/1,M10.5.0",
+thus swapping standard and daylight saving time.
+Although this workaround misidentifies which part of the year
+uses daylight saving time, it records UT offsets and time zone
+abbreviations correctly.
+.PP
+Some interoperability problems are reader bugs that
+are listed here mostly as warnings to developers of readers.
+.IP * 2
+Some readers do not support negative timestamps.
+Developers of distributed applications should keep this
+in mind if they need to deal with pre-1970 data.
+.IP *
+Some readers mishandle timestamps before the first
+transition that has a nonnegative timestamp.
+Readers that do not support negative timestamps are likely to
+be more prone to this problem.
+.IP *
+Some readers mishandle time zone abbreviations like
+.q "-08"
+that contain
+.q "+",
+.q "-",
+or digits.
+.IP *
+Some readers mishandle UT offsets that are out of the
+traditional range of \*-12 through +12 hours, and so do not
+support locations like Kiritimati that are outside this
+range.
+.IP *
+Some readers mishandle UT offsets in the range [\*-3599, \*-1]
+seconds from UT, because they integer-divide the offset by
+3600 to get 0 and then display the hour part as
+.q "+00".
+.IP *
+Some readers mishandle UT offsets that are not a multiple
+of one hour, or of 15 minutes, or of 1 minute.
 .SH SEE ALSO
 .BR time (2),
 .BR localtime (3),
diff --git a/tz/zdump.8 b/tz/zdump.8
index f369056..fb6b8df 100644
--- a/tz/zdump.8
+++ b/tz/zdump.8
@@ -150,15 +150,16 @@ tabbed columns line up.)
 .if \n(.g .ft CW
 .if t .in +.5i
 .if n .in +2
-.nr w \w'1896-01-13 'u
-.ta \nwu +\nwu +\nwu +\nwu
+.nr w \w'1896-01-13  'u+\n(.i
+.ta \w'1896-01-13  'u +\w'12:01:26  'u +\w'-103126  'u +\w'HWT  'u
 TZ="Pacific/Honolulu"
--	-	-10:31:26	LMT
-1896-01-13	12:01:26	-10:30	HST
-1933-04-30	03	-09:30	HDT	1
-1933-05-21	11	-10:30	HST
-1942-02-09	03	-09:30	HDT	1
-1945-09-30	01	-10:30	HST
+-	-	-103126	LMT
+1896-01-13	12:01:26	-1030	HST
+1933-04-30	03	-0930	HDT	1
+1933-05-21	11	-1030	HST
+1942-02-09	03	-0930	HWT	1
+1945-08-14	13:30	-0930	HPT	1
+1945-09-30	01	-1030	HST
 1947-06-08	02:30	-10	HST
 .in
 .if \n(.g .ft
@@ -183,7 +184,7 @@ Here are excerpts from another example:
 .if t .in +.5i
 .if n .in +2
 TZ="Europe/Astrakhan"
--	-	+03:12:12	LMT
+-	-	+031212	LMT
 1924-04-30	23:47:48	+03
 1930-06-21	01	+04
 1981-04-01	01	+05		1
diff --git a/tz/zic.8 b/tz/zic.8
index c277d9c..ac85e46 100644
--- a/tz/zic.8
+++ b/tz/zic.8
@@ -304,6 +304,10 @@ or
 if the given time is universal time;
 in the absence of an indicator,
 wall clock time is assumed.
+These forms ignore leap seconds; for example,
+if a leap second occurs at 00:59:60 local time,
+.q "1:00"
+stands for 3601 seconds after local midnight instead of the usual 3600 seconds.
 The intent is that a rule line describes the instants when a
 clock/calendar set to the type of time specified in the
 .B AT
diff --git a/tz/zic.c b/tz/zic.c
index 06becc2..cb1bf28 100644
--- a/tz/zic.c
+++ b/tz/zic.c
@@ -64,6 +64,11 @@ typedef int_fast64_t	zic_t;
 static ptrdiff_t const PTRDIFF_MAX = MAXVAL(ptrdiff_t, TYPE_BIT(ptrdiff_t));
 #endif
 
+/* The minimum alignment of a type, for pre-C11 platforms.  */
+#if __STDC_VERSION__ < 201112
+# define _Alignof(type) offsetof(struct { char a; type b; }, b)
+#endif
+
 /* The type for line numbers.  Use PRIdMAX to format them; formerly
    there was also "#define PRIdLINENO PRIdMAX" and formats used
    PRIdLINENO, but xgettext cannot grok that.  */
@@ -189,7 +194,9 @@ enum { PERCENT_Z_LEN_BOUND = sizeof "+995959" - 1 };
    QTBUG-53071 <https://bugreports.qt.io/browse/QTBUG-53071>.  This
    workaround will no longer be needed when Qt 5.6.1 and earlier are
    obsolete, say in the year 2021.  */
+#ifndef WORK_AROUND_QTBUG_53071
 enum { WORK_AROUND_QTBUG_53071 = true };
+#endif
 
 static int		charcnt;
 static bool		errors;
@@ -431,6 +438,16 @@ size_product(size_t nitems, size_t itemsize)
 	return nitems * itemsize;
 }
 
+static ATTRIBUTE_PURE size_t
+align_to(size_t size, size_t alignment)
+{
+  size_t aligned_size = size + alignment - 1;
+  aligned_size -= aligned_size % alignment;
+  if (aligned_size < size)
+    memory_exhausted(_("alignment overflow"));
+  return aligned_size;
+}
+
 #if !HAVE_STRDUP
 static char *
 strdup(char const *str)
@@ -1714,12 +1731,6 @@ atcomp(const void *avp, const void *bvp)
 	return (a < b) ? -1 : (a > b);
 }
 
-static bool
-is32(const zic_t x)
-{
-	return INT32_MIN <= x && x <= INT32_MAX;
-}
-
 static void
 swaptypes(int i, int j)
 {
@@ -1746,7 +1757,11 @@ writezone(const char *const name, const char *const string, char version,
 	zic_t one = 1;
 	zic_t y2038_boundary = one << 31;
 	ptrdiff_t nats = timecnt + WORK_AROUND_QTBUG_53071;
-	zic_t *ats = emalloc(size_product(nats, sizeof *ats + 1));
+
+	/* Allocate the ATS and TYPES arrays via a single malloc,
+	   as this is a bit faster.  */
+	zic_t *ats = emalloc(align_to(size_product(nats, sizeof *ats + 1),
+				      _Alignof(zic_t)));
 	void *typesptr = ats + nats;
 	unsigned char *types = typesptr;
 
@@ -1797,18 +1812,6 @@ writezone(const char *const name, const char *const string, char version,
 		types[i] = attypes[i].type;
 	}
 
-	/* Work around QTBUG-53071 for timestamps less than y2038_boundary - 1,
-	   by inserting a no-op transition at time y2038_boundary - 1.
-	   This works only for timestamps before the boundary, which
-	   should be good enough in practice as QTBUG-53071 should be
-	   long-dead by 2038.  */
-	if (WORK_AROUND_QTBUG_53071 && timecnt != 0
-	    && ats[timecnt - 1] < y2038_boundary - 1 && strchr(string, '<')) {
-	  ats[timecnt] = y2038_boundary - 1;
-	  types[timecnt] = types[timecnt - 1];
-	  timecnt++;
-	}
-
 	/*
 	** Correct for leap seconds.
 	*/
@@ -1820,6 +1823,22 @@ writezone(const char *const name, const char *const string, char version,
 				break;
 			}
 	}
+
+	/* Work around QTBUG-53071 for timestamps less than y2038_boundary - 1,
+	   by inserting a no-op transition at time y2038_boundary - 1.
+	   This works only for timestamps before the boundary, which
+	   should be good enough in practice as QTBUG-53071 should be
+	   long-dead by 2038.  Do this after correcting for leap
+	   seconds, as the idea is to insert a transition just before
+	   32-bit time_t rolls around, and this occurs at a slightly
+	   different moment if transitions are leap-second corrected.  */
+	if (WORK_AROUND_QTBUG_53071 && timecnt != 0
+	    && ats[timecnt - 1] < y2038_boundary - 1 && strchr(string, '<')) {
+	  ats[timecnt] = y2038_boundary - 1;
+	  types[timecnt] = types[timecnt - 1];
+	  timecnt++;
+	}
+
 	/*
 	** Figure out 32-bit-limited starts and counts.
 	*/
@@ -1827,22 +1846,22 @@ writezone(const char *const name, const char *const string, char version,
 	timei32 = 0;
 	leapcnt32 = leapcnt;
 	leapi32 = 0;
-	while (timecnt32 > 0 && !is32(ats[timecnt32 - 1]))
+	while (0 < timecnt32 && INT32_MAX < ats[timecnt32 - 1])
 		--timecnt32;
-	while (timecnt32 > 0 && !is32(ats[timei32])) {
+	while (1 < timecnt32 && ats[timei32] < INT32_MIN
+	       && ats[timei32 + 1] <= INT32_MIN) {
+		/* Discard too-low transitions, except keep any last too-low
+		   transition if no transition is exactly at INT32_MIN.
+		   The kept transition will be output as an INT32_MIN
+		   "transition" appropriate for buggy 32-bit clients that do
+		   not use time type 0 for timestamps before the first
+		   transition; see below.  */
 		--timecnt32;
 		++timei32;
 	}
-	/*
-	** Output an INT32_MIN "transition" if appropriate; see below.
-	*/
-	if (timei32 > 0 && ats[timei32] > INT32_MIN) {
-		--timei32;
-		++timecnt32;
-	}
-	while (leapcnt32 > 0 && !is32(trans[leapcnt32 - 1]))
+	while (0 < leapcnt32 && INT32_MAX < trans[leapcnt32 - 1])
 		--leapcnt32;
-	while (leapcnt32 > 0 && !is32(trans[leapi32])) {
+	while (0 < leapcnt32 && trans[leapi32] < INT32_MIN) {
 		--leapcnt32;
 		++leapi32;
 	}
diff --git a/tz/ziguard.awk b/tz/ziguard.awk
index 42e2910..e3c7298 100644
--- a/tz/ziguard.awk
+++ b/tz/ziguard.awk
@@ -80,6 +80,13 @@ DATAFORM != "main" {
   if (comment_out) {
     sub(/^/, "#")
   }
+
+  # In rearguard format, change the Japan rule line with "Sat>=8 25:00"
+  # to "Sun>=9 1:00", to cater to zic before 2007 and to older Java.
+  if (!vanguard && $1 == "Rule" && $7 == "Sat>=8" && $8 == "25:00") {
+    sub(/Sat>=8/, "Sun>=9")
+    sub(/25:00/, " 1:00")
+  }
 }
 
 # If a Link line is followed by a Zone line for the same data, comment
diff --git a/tz/zishrink.awk b/tz/zishrink.awk
index 74e0de9..8876b68 100644
--- a/tz/zishrink.awk
+++ b/tz/zishrink.awk
@@ -172,11 +172,6 @@ function process_input_line(line, field, end, i, n, startdef)
     if (line ~ /^R /) return
     line = substr(line, 1, RSTART) substr(line, RSTART + 5)
   }
-  # Replace SpainAfrica rules with Morocco, as they are duplicates.
-  if (match(line, / SpainAfrica /)) {
-    if (line ~ /^R /) return
-    line = substr(line, 1, RSTART) "Morocco" substr(line, RSTART + RLENGTH - 1)
-  }
 
   # Abbreviate times.
   while (match(line, /[: ]0+[0-9]/))