IANA 2020a

23 files changed, 672 insertions, 257 deletions

diff --git a/tz/Makefile b/tz/Makefile
index fec0a4f..610bf19 100644
--- a/tz/Makefile
+++ b/tz/Makefile
@@ -150,6 +150,15 @@ TIME_T_ALTERNATIVES_TAIL = int32_t uint32_t uint64_t
 
 REDO=		posix_right
 
+# Whether to put an "Expires" line in the leapseconds file.
+# Use EXPIRES_LINE=1 to put the line in, 0 to omit it.
+# The EXPIRES_LINE value matters only if REDO's value contains "right".
+# If you change EXPIRES_LINE, remove the leapseconds file before running "make".
+# zic's support for the Expires line was introduced in tzdb 2020a,
+# and EXPIRES_LINE defaults to 0 for now so that the leapseconds file
+# can be given to older zic implementations.
+EXPIRES_LINE=	0
+
 # To install data in text form that has all the information of the TZif data,
 # (optionally incorporating leap second information), use
 #	TZDATA_TEXT=	tzdata.zi leapseconds
@@ -295,8 +304,9 @@ GCC_DEBUG_FLAGS = -DGCC_LINT -g3 -O3 -fno-common \
 # than TM_GMTOFF and TM_ZONE.  However, most of them are standardized.
 # #
 # # To omit or support the external variable "tzname", add one of:
-# #	-DHAVE_TZNAME=0
-# #	-DHAVE_TZNAME=1
+# #	-DHAVE_TZNAME=0 # do not support "tzname"
+# #	-DHAVE_TZNAME=1 # support "tzname", which is defined by system library
+# #	-DHAVE_TZNAME=2 # support and define "tzname"
 # # to the "CFLAGS=" line.  "tzname" is required by POSIX 1988 and later.
 # # If not defined, the code attempts to guess HAVE_TZNAME from other macros.
 # # Warning: unless time_tz is also defined, HAVE_TZNAME=1 can cause
@@ -304,16 +314,20 @@ GCC_DEBUG_FLAGS = -DGCC_LINT -g3 -O3 -fno-common \
 # # presumably due to memory allocation issues.
 # #
 # # To omit or support the external variables "timezone" and "daylight", add
-# #	-DUSG_COMPAT=0
-# #	-DUSG_COMPAT=1
+# #	-DUSG_COMPAT=0 # do not support
+# #	-DUSG_COMPAT=1 # support, and variables are defined by system library
+# #	-DUSG_COMPAT=2 # support and define variables
 # # to the "CFLAGS=" line; "timezone" and "daylight" are inspired by
 # # Unix Systems Group code and are required by POSIX 2008 (with XSI) and later.
 # # If not defined, the code attempts to guess USG_COMPAT from other macros.
 # #
 # # To support the external variable "altzone", add
-# #	-DALTZONE
+# #	-DALTZONE=0 # do not support
+# #	-DALTZONE=1 # support "altzone", which is defined by system library
+# #	-DALTZONE=2 # support and define "altzone"
 # # to the end of the "CFLAGS=" line; although "altzone" appeared in
 # # System V Release 3.1 it has not been standardized.
+# # If not defined, the code attempts to guess ALTZONE from other macros.
 #
 # If you want functions that were inspired by early versions of X3J11's work,
 # add
@@ -321,9 +335,7 @@ GCC_DEBUG_FLAGS = -DGCC_LINT -g3 -O3 -fno-common \
 # to the end of the "CFLAGS=" line.  This arranges for the functions
 # "tzsetwall", "offtime", "timelocal", "timegm", "timeoff",
 # "posix2time", and "time2posix" to be added to the time conversion library.
-# "tzsetwall" is like "tzset" except that it arranges for local wall clock
-# time (rather than the timezone specified in the TZ environment variable)
-# to be used.
+# "tzsetwall" is deprecated and is intended to be removed soon; see NEWS.
 # "offtime" is like "gmtime" except that it accepts a second (long) argument
 # that gives an offset to add to the time_t when converting it.
 # "timelocal" is equivalent to "mktime".
@@ -333,7 +345,6 @@ GCC_DEBUG_FLAGS = -DGCC_LINT -g3 -O3 -fno-common \
 # that gives an offset to use when converting to a time_t.
 # "posix2time" and "time2posix" are described in an included manual page.
 # X3J11's work does not describe any of these functions.
-# Sun has provided "tzsetwall", "timelocal", and "timegm" in SunOS 4.0.
 # These functions may well disappear in future releases of the time
 # conversion package.
 #
@@ -505,11 +516,11 @@ RANLIB=		:
 TZCOBJS=	zic.o
 TZDOBJS=	zdump.o localtime.o asctime.o strftime.o
 DATEOBJS=	date.o localtime.o strftime.o asctime.o
-LIBSRCS=	localtime.c asctime.c difftime.c
-LIBOBJS=	localtime.o asctime.o difftime.o
+LIBSRCS=	localtime.c asctime.c difftime.c strftime.c
+LIBOBJS=	localtime.o asctime.o difftime.o strftime.o
 HEADERS=	tzfile.h private.h
 NONLIBSRCS=	zic.c zdump.c
-NEWUCBSRCS=	date.c strftime.c
+NEWUCBSRCS=	date.c
 SOURCES=	$(HEADERS) $(LIBSRCS) $(NONLIBSRCS) $(NEWUCBSRCS) \
 			tzselect.ksh workman.sh
 MANS=		newctime.3 newstrftime.3 newtzset.3 time2posix.3 \
@@ -651,7 +662,8 @@ yearistype:	yearistype.sh
 		chmod +x yearistype
 
 leapseconds:	$(LEAP_DEPS)
-		$(AWK) -f leapseconds.awk leap-seconds.list >$@.out
+		$(AWK) -v EXPIRES_LINE=$(EXPIRES_LINE) \
+		  -f leapseconds.awk leap-seconds.list >$@.out
 		mv $@.out $@
 
 # Arguments to pass to submakes of install_data.
diff --git a/tz/NEWS b/tz/NEWS
index af0f06f..321e090 100644
--- a/tz/NEWS
+++ b/tz/NEWS
@@ -1,5 +1,87 @@
 News for the tz database
 
+Release 2020a - 2020-04-23 16:03:47 -0700
+
+  Briefly:
+    Morocco springs forward on 2020-05-31, not 2020-05-24.
+    Canada's Yukon advanced to -07 year-round on 2020-03-08.
+    America/Nuuk renamed from America/Godthab.
+    zic now supports expiration dates for leap second lists.
+
+  Changes to future timestamps
+
+    Morocco's second spring-forward transition in 2020 will be May 31,
+    not May 24 as predicted earlier.  (Thanks to Semlali Naoufal.)
+    Adjust future-year predictions to use the first Sunday after the
+    day after Ramadan, not the first Sunday after Ramadan.
+
+    Canada's Yukon, represented by America/Whitehorse and
+    America/Dawson, advanced to -07 year-round, beginning with its
+    spring-forward transition on 2020-03-08, and will not fall back on
+    2020-11-01.  Although a government press release calls this
+    "permanent Pacific Daylight Saving Time", we prefer MST for
+    consistency with nearby Dawson Creek, Creston, and Fort Nelson.
+    (Thanks to Tim Parenti.)
+
+  Changes to past timestamps
+
+    Shanghai observed DST in 1919.  (Thanks to Phake Nick.)
+
+  Changes to timezone identifiers
+
+    To reflect current usage in English better, America/Godthab has
+    been renamed to America/Nuuk.  A backwards-compatibility link
+    remains for the old name.
+
+  Changes to code
+
+    localtime.c no longer mishandles timestamps after the last
+    transition in a TZif file with leap seconds and with daylight
+    saving time transitions projected into the indefinite future.
+    For example, with TZ='America/Los_Angeles' with leap seconds,
+    zdump formerly reported a DST transition on 2038-03-14
+    from 01:59:32.999... to 02:59:33 instead of the correct transition
+    from 01:59:59.999... to 03:00:00.
+
+    zic -L now supports an Expires line in the leapseconds file, and
+    truncates the TZif output accordingly.  This propagates leap
+    second expiration information into the TZif file, and avoids the
+    abovementioned localtime.c bug as well as similar bugs present in
+    many client implementations.  If no Expires line is present, zic
+    -L instead truncates the TZif output based on the #expires comment
+    present in leapseconds files distributed by tzdb 2018f and later;
+    however, this usage is obsolescent.  For now, the distributed
+    leapseconds file has an Expires line that is commented out, so
+    that the file can be fed to older versions of zic which ignore the
+    commented-out line.  Future tzdb distributions are planned to
+    contain a leapseconds file with an Expires line.
+
+    The configuration macros HAVE_TZNAME and USG_COMPAT should now be
+    set to 1 if the system library supports the feature, and 2 if not.
+    As before, these macros are nonzero if tzcode should support the
+    feature, zero otherwise.
+
+    The configuration macro ALTZONE now has the same values with the
+    same meaning as HAVE_TZNAME and USG_COMPAT.
+
+    The code's defense against CRLF in leap-seconds.list is now
+    portable to POSIX awk.  (Problem reported by Deborah Goldsmith.)
+
+    Although the undocumented tzsetwall function is not changed in
+    this release, it is now deprecated in preparation for removal in
+    future releases.  Due to POSIX requirements, tzsetwall has not
+    worked for some time.  Any code that uses it should instead use
+    tzalloc(NULL) or, if portability trumps thread-safety, should
+    unset the TZ environment variable.
+
+  Changes to commentary
+
+    The Îles-de-la-Madeleine and the Listuguj reserve are noted as
+    following America/Halifax, and comments about Yukon's "south" and
+    "north" have been corrected to say "east" and "west".  (Thanks to
+    Jeffery Nichols.)
+
+
 Release 2019c - 2019-09-11 08:59:48 -0700
 
   Briefly:
diff --git a/tz/africa b/tz/africa
index feb6017..724744f 100644
--- a/tz/africa
+++ b/tz/africa
@@ -867,19 +867,25 @@ Zone Indian/Mauritius	3:50:00 -	LMT	1907 # Port Louis
 # Morocco will be on GMT starting from Sunday, May 5th 2019 at 3am.
 # The switch to GMT+1 will occur on Sunday, June 9th 2019 at 2am....
 # http://fr.le360.ma/societe/voici-la-date-du-retour-a-lheure-legale-au-maroc-188222
-#
-# From Paul Eggert (2019-05-20):
-# This agrees with our 2018-11-01 guess that the Moroccan government
-# would continue the practice of falling back at 03:00 the last Sunday
-# before Ramadan, and of springing forward at 02:00 the first Sunday after
-# Ramadan, as this has been the practice since 2012.  To implement this,
-# transition dates for 2019 through 2087 were determined by running the
-# following program under GNU Emacs 26.2.
-# (let ((islamic-year 1440))
+
+# From Semlali Naoufal (2020-04-14):
+# Following the announcement by the Moroccan government, the switch to
+# GMT time will take place on Sunday, April 19, 2020 from 3 a.m. and
+# the return to GMT+1 time will take place on Sunday, May 31, 2020 at 2 a.m....
+# https://maroc-diplomatique.net/maroc-le-retour-a-lheure-gmt-est-prevu-dimanche-prochain/
+# http://aujourdhui.ma/actualite/gmt1-retour-a-lheure-normale-dimanche-prochain-1
+#
+# From Paul Eggert (2020-04-14):
+# For now, guess that in the future Morocco will fall back at 03:00
+# the last Sunday before Ramadan, and spring forward at 02:00 the
+# first Sunday after the day after Ramadan.  To implement this,
+# transition dates for 2021 through 2087 were determined by running
+# the following program under GNU Emacs 26.3.
+# (let ((islamic-year 1442))
 #   (require 'cal-islam)
 #   (while (< islamic-year 1511)
 #     (let ((a (calendar-islamic-to-absolute (list 9 1 islamic-year)))
-#           (b (calendar-islamic-to-absolute (list 10 1 islamic-year)))
+#           (b (1+ (calendar-islamic-to-absolute (list 10 1 islamic-year))))
 #           (sunday 0))
 #       (while (/= sunday (mod (setq a (1- a)) 7)))
 #       (while (/= sunday (mod b 7))
@@ -939,7 +945,7 @@ Rule	Morocco	2018	only	-	Jun	17	 2:00	1:00	-
 Rule	Morocco	2019	only	-	May	 5	 3:00	-1:00	-
 Rule	Morocco	2019	only	-	Jun	 9	 2:00	0	-
 Rule	Morocco	2020	only	-	Apr	19	 3:00	-1:00	-
-Rule	Morocco	2020	only	-	May	24	 2:00	0	-
+Rule	Morocco	2020	only	-	May	31	 2:00	0	-
 Rule	Morocco	2021	only	-	Apr	11	 3:00	-1:00	-
 Rule	Morocco	2021	only	-	May	16	 2:00	0	-
 Rule	Morocco	2022	only	-	Mar	27	 3:00	-1:00	-
@@ -955,7 +961,7 @@ Rule	Morocco	2026	only	-	Mar	22	 2:00	0	-
 Rule	Morocco	2027	only	-	Feb	 7	 3:00	-1:00	-
 Rule	Morocco	2027	only	-	Mar	14	 2:00	0	-
 Rule	Morocco	2028	only	-	Jan	23	 3:00	-1:00	-
-Rule	Morocco	2028	only	-	Feb	27	 2:00	0	-
+Rule	Morocco	2028	only	-	Mar	 5	 2:00	0	-
 Rule	Morocco	2029	only	-	Jan	14	 3:00	-1:00	-
 Rule	Morocco	2029	only	-	Feb	18	 2:00	0	-
 Rule	Morocco	2029	only	-	Dec	30	 3:00	-1:00	-
@@ -971,7 +977,7 @@ Rule	Morocco	2033	only	-	Dec	25	 2:00	0	-
 Rule	Morocco	2034	only	-	Nov	 5	 3:00	-1:00	-
 Rule	Morocco	2034	only	-	Dec	17	 2:00	0	-
 Rule	Morocco	2035	only	-	Oct	28	 3:00	-1:00	-
-Rule	Morocco	2035	only	-	Dec	 2	 2:00	0	-
+Rule	Morocco	2035	only	-	Dec	 9	 2:00	0	-
 Rule	Morocco	2036	only	-	Oct	19	 3:00	-1:00	-
 Rule	Morocco	2036	only	-	Nov	23	 2:00	0	-
 Rule	Morocco	2037	only	-	Oct	 4	 3:00	-1:00	-
@@ -987,7 +993,7 @@ Rule	Morocco	2041	only	-	Sep	29	 2:00	0	-
 Rule	Morocco	2042	only	-	Aug	10	 3:00	-1:00	-
 Rule	Morocco	2042	only	-	Sep	21	 2:00	0	-
 Rule	Morocco	2043	only	-	Aug	 2	 3:00	-1:00	-
-Rule	Morocco	2043	only	-	Sep	 6	 2:00	0	-
+Rule	Morocco	2043	only	-	Sep	13	 2:00	0	-
 Rule	Morocco	2044	only	-	Jul	24	 3:00	-1:00	-
 Rule	Morocco	2044	only	-	Aug	28	 2:00	0	-
 Rule	Morocco	2045	only	-	Jul	 9	 3:00	-1:00	-
@@ -1003,7 +1009,7 @@ Rule	Morocco	2049	only	-	Jul	 4	 2:00	0	-
 Rule	Morocco	2050	only	-	May	15	 3:00	-1:00	-
 Rule	Morocco	2050	only	-	Jun	26	 2:00	0	-
 Rule	Morocco	2051	only	-	May	 7	 3:00	-1:00	-
-Rule	Morocco	2051	only	-	Jun	11	 2:00	0	-
+Rule	Morocco	2051	only	-	Jun	18	 2:00	0	-
 Rule	Morocco	2052	only	-	Apr	28	 3:00	-1:00	-
 Rule	Morocco	2052	only	-	Jun	 2	 2:00	0	-
 Rule	Morocco	2053	only	-	Apr	13	 3:00	-1:00	-
@@ -1019,7 +1025,7 @@ Rule	Morocco	2057	only	-	Apr	 8	 2:00	0	-
 Rule	Morocco	2058	only	-	Feb	17	 3:00	-1:00	-
 Rule	Morocco	2058	only	-	Mar	31	 2:00	0	-
 Rule	Morocco	2059	only	-	Feb	 9	 3:00	-1:00	-
-Rule	Morocco	2059	only	-	Mar	16	 2:00	0	-
+Rule	Morocco	2059	only	-	Mar	23	 2:00	0	-
 Rule	Morocco	2060	only	-	Feb	 1	 3:00	-1:00	-
 Rule	Morocco	2060	only	-	Mar	 7	 2:00	0	-
 Rule	Morocco	2061	only	-	Jan	16	 3:00	-1:00	-
@@ -1029,13 +1035,13 @@ Rule	Morocco	2062	only	-	Feb	12	 2:00	0	-
 Rule	Morocco	2062	only	-	Dec	31	 3:00	-1:00	-
 Rule	Morocco	2063	only	-	Feb	 4	 2:00	0	-
 Rule	Morocco	2063	only	-	Dec	16	 3:00	-1:00	-
-Rule	Morocco	2064	only	-	Jan	20	 2:00	0	-
+Rule	Morocco	2064	only	-	Jan	27	 2:00	0	-
 Rule	Morocco	2064	only	-	Dec	 7	 3:00	-1:00	-
 Rule	Morocco	2065	only	-	Jan	11	 2:00	0	-
 Rule	Morocco	2065	only	-	Nov	22	 3:00	-1:00	-
 Rule	Morocco	2066	only	-	Jan	 3	 2:00	0	-
 Rule	Morocco	2066	only	-	Nov	14	 3:00	-1:00	-
-Rule	Morocco	2066	only	-	Dec	19	 2:00	0	-
+Rule	Morocco	2066	only	-	Dec	26	 2:00	0	-
 Rule	Morocco	2067	only	-	Nov	 6	 3:00	-1:00	-
 Rule	Morocco	2067	only	-	Dec	11	 2:00	0	-
 Rule	Morocco	2068	only	-	Oct	21	 3:00	-1:00	-
@@ -1045,13 +1051,13 @@ Rule	Morocco	2069	only	-	Nov	17	 2:00	0	-
 Rule	Morocco	2070	only	-	Oct	 5	 3:00	-1:00	-
 Rule	Morocco	2070	only	-	Nov	 9	 2:00	0	-
 Rule	Morocco	2071	only	-	Sep	20	 3:00	-1:00	-
-Rule	Morocco	2071	only	-	Oct	25	 2:00	0	-
+Rule	Morocco	2071	only	-	Nov	 1	 2:00	0	-
 Rule	Morocco	2072	only	-	Sep	11	 3:00	-1:00	-
 Rule	Morocco	2072	only	-	Oct	16	 2:00	0	-
 Rule	Morocco	2073	only	-	Aug	27	 3:00	-1:00	-
 Rule	Morocco	2073	only	-	Oct	 8	 2:00	0	-
 Rule	Morocco	2074	only	-	Aug	19	 3:00	-1:00	-
-Rule	Morocco	2074	only	-	Sep	23	 2:00	0	-
+Rule	Morocco	2074	only	-	Sep	30	 2:00	0	-
 Rule	Morocco	2075	only	-	Aug	11	 3:00	-1:00	-
 Rule	Morocco	2075	only	-	Sep	15	 2:00	0	-
 Rule	Morocco	2076	only	-	Jul	26	 3:00	-1:00	-
@@ -1061,7 +1067,7 @@ Rule	Morocco	2077	only	-	Aug	22	 2:00	0	-
 Rule	Morocco	2078	only	-	Jul	10	 3:00	-1:00	-
 Rule	Morocco	2078	only	-	Aug	14	 2:00	0	-
 Rule	Morocco	2079	only	-	Jun	25	 3:00	-1:00	-
-Rule	Morocco	2079	only	-	Jul	30	 2:00	0	-
+Rule	Morocco	2079	only	-	Aug	 6	 2:00	0	-
 Rule	Morocco	2080	only	-	Jun	16	 3:00	-1:00	-
 Rule	Morocco	2080	only	-	Jul	21	 2:00	0	-
 Rule	Morocco	2081	only	-	Jun	 1	 3:00	-1:00	-
@@ -1077,7 +1083,7 @@ Rule	Morocco	2085	only	-	May	27	 2:00	0	-
 Rule	Morocco	2086	only	-	Apr	14	 3:00	-1:00	-
 Rule	Morocco	2086	only	-	May	19	 2:00	0	-
 Rule	Morocco	2087	only	-	Mar	30	 3:00	-1:00	-
-Rule	Morocco	2087	only	-	May	 4	 2:00	0	-
+Rule	Morocco	2087	only	-	May	11	 2:00	0	-
 # For dates after the somewhat-arbitrary cutoff of 2087, assume that
 # Morocco will no longer observe DST.  At some point this table will
 # need to be extended, though quite possibly Morocco will change the
@@ -1179,7 +1185,7 @@ Link Africa/Maputo Africa/Lusaka	# Zambia
 Rule	Namibia	1994	only	-	Mar	21	0:00	-1:00	WAT
 Rule	Namibia	1994	2017	-	Sep	Sun>=1	2:00	0	CAT
 Rule	Namibia	1995	2017	-	Apr	Sun>=1	2:00	-1:00	WAT
-# Rearguard section, for parsers that do not support negative DST.
+# Rearguard section, for parsers lacking negative DST; see ziguard.awk.
 #Rule	Namibia	1994	only	-	Mar	21	0:00	0	WAT
 #Rule	Namibia	1994	2017	-	Sep	Sun>=1	2:00	1:00	CAT
 #Rule	Namibia	1995	2017	-	Apr	Sun>=1	2:00	0	WAT
@@ -1193,7 +1199,7 @@ Zone	Africa/Windhoek	1:08:24 -	LMT	1892 Feb 8
 			2:00	-	SAST	1990 Mar 21 # independence
 # Vanguard section, for zic and other parsers that support negative DST.
 			2:00	Namibia	%s
-# Rearguard section, for parsers that do not support negative DST.
+# Rearguard section, for parsers lacking negative DST; see ziguard.awk.
 #			2:00	-	CAT	1994 Mar 21  0:00
 # From Paul Eggert (2017-04-07):
 # The official date of the 2017 rule change was 2017-10-24.  See:
diff --git a/tz/asia b/tz/asia
index b29c896..106efad 100644
--- a/tz/asia
+++ b/tz/asia
@@ -286,6 +286,27 @@ Zone	Asia/Yangon	6:24:47 -	LMT	1880        # or Rangoon
 
 # China
 
+# From Phake Nick (2020-04-15):
+# According to this news report:
+# http://news.sina.com.cn/c/2004-09-01/19524201403.shtml
+# on April 11, 1919, newspaper in Shanghai said clocks in Shanghai will spring
+# forward for an hour starting from midnight of that Saturday. The report did
+# not mention what happened in Shanghai thereafter, but it mentioned that a
+# similar trial in Tianjin which ended at October 1st as citizens are told to
+# recede the clock on September 30 from 12:00pm to 11:00pm. The trial at
+# Tianjin got terminated in 1920.
+#
+# From Paul Eggert (2020-04-15):
+# The Returns of Trade and Trade Reports, page 711, says "Daylight saving was
+# given a trial during the year, and from the 12th April to the 1st October
+# the clocks were all set one hour ahead of sun time.  Though the scheme was
+# generally esteemed a success, it was announced early in 1920 that it would
+# not be repeated."
+#
+# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
+Rule	Shang	1919	only	-	Apr	12	24:00	1:00	D
+Rule	Shang	1919	only	-	Sep	30	24:00	0	S
+
 # From Paul Eggert (2018-10-02):
 # The following comes from Table 1 of:
 # Li Yu. Research on the daylight saving movement in 1940s Shanghai.
@@ -294,6 +315,89 @@ Zone	Asia/Yangon	6:24:47 -	LMT	1880        # or Rangoon
 # The table lists dates only; I am guessing 00:00 and 24:00 transition times.
 # Also, the table lists the planned end of DST in 1949, but the corresponding
 # zone line cuts this off on May 28, when the Communists took power.
+
+# From Phake Nick (2020-04-15):
+#
+# For the history of time in Shanghai between 1940-1942, the situation is
+# actually slightly more complex than the table [below]....  At the time,
+# there were three different authorities in Shanghai, including Shanghai
+# International Settlement, a settlement established by western countries with
+# its own westernized form of government, Shanghai French Concession, similar
+# to the international settlement but is controlled by French, and then the
+# rest of the city of Shanghai, which have already been controlled by Japanese
+# force through a puppet local government (Wang Jingwei regime).  It was
+# additionally complicated by the circumstances that, according to the 1940s
+# Shanghai summer time essay cited in the database, some
+# departments/businesses/people in the Shanghai city itself during that time
+# period, refused to change their clock and instead only changed their opening
+# hours.
+#
+# For example, as quoted in the article, in 1940, other than the authority
+# itself, power, tram, bus companies, cinema, department stores, and other
+# public service organizations have all decided to follow the summer time and
+# spring forward the clock.  On the other hand, the custom office refused to
+# spring forward the clock because of worry on mechanical wear to the physical
+# clock, postal office refused to spring forward because of disruption to
+# business and log-keeping, although they did changed their office hour to
+# match rest of the city.  So is travel agents, and also weather
+# observatory.  It is said both time standards had their own supporters in the
+# city at the time, those who prefer new time standard would have moved their
+# clock while those who prefer the old time standard would keep their clock
+# unchange, and there were different clocks that use different time standard
+# in the city at the time for people who use different time standard to adjust
+# their clock to their preferred time.
+#
+# a. For the 1940 May 31 spring forward, the essay claim that it was
+# coordinared between the international settlement authority and the French
+# concession authority and have gathered support from Hong Kong and Xiamen,
+# that it would spring forward an hour from May 31 "midnight", and the essay
+# claim "Hong Kong government implemented the spring forward in the same time
+# on the same date as Shanghai".
+#
+# b. For the 1940 fall back, it was said that they initially intended to do
+# so on September 30 00:59 at night, however they postponed it to October 12
+# after discussion with relevant parties. However schools restored to the
+# original schedule ten days earlier.
+#
+# c. For the 1941 spring forward, it is said to start from March 15
+# "following the previous year's method", and in addition to that the essay
+# cited an announcement in 1941 from the Wang regime which said the Special
+# City of Shanghai under Wang regime control will follow the DST rule set by
+# the Settlements, irrespective of the original DST plan announced by the Wang
+# regime for other area under its control(April 1 to September 30). (no idea
+# to situation before that announcement)
+#
+# d. For the 1941 fall back, it was said that the fall back would occurs at
+# the end of September (A newspaper headline cited by the essay, published on
+# October 1, 1941, have the headlines which said "French Concession would
+# rewind to the old clock this morning), but it ultimately didn't happen due
+# to disagreement between the international settlement authority and the
+# French concession authority, and the fall back ultimately occurred on
+# November 1.
+#
+# e. In 1941 December, Japan have officially started war with the United
+# States and the United Kingdom, and in Shanghai they have marched into the
+# international settlement, taken over its control
+#
+# f. For the 1942 spring forward, the essay said that the spring forward
+# started on January 31. It said this time the custom office and postal
+# department will also change their clocks, unlike before.
+#
+# g. The essay itself didn't cover any specific changes thereafter until the
+# end of the war, it quoted a November 1942 command from the government of the
+# Wang regime, which claim the daylight saving time applies year round during
+# the war. However, the essay ambiguously said the period is "February 1 to
+# September 30", which I don't really understand what is the meaning of such
+# period in the context of year round implementation here.. More researches
+# might be needed to show exactly what happened during that period of time.
+
+# From Phake Nick (2020-04-15):
+# According to a Japanese tour bus pamphlet in Nanjing area believed to be
+# from around year 1941: http://www.tt-museum.jp/tairiku_0280_nan1941.html ,
+# the schedule listed was in the format of Japanese time.  Which indicate some
+# use of the Japanese time (instead of syncing by DST) might have occurred in
+# the Yangtze river delta area during that period of time although the scope
+# of such use will need to be investigated to determine.
 #
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 Rule	Shang	1940	only	-	Jun	 1	 0:00	1:00	D
@@ -572,7 +676,7 @@ Zone	Asia/Urumqi	5:50:20	-	LMT	1928
 			6:00	-	+06
 
 
-# Hong Kong (Xianggang)
+# Hong Kong
 
 # Milne gives 7:36:41.7; round this.
 
@@ -582,9 +686,7 @@ Zone	Asia/Urumqi	5:50:20	-	LMT	1928
 # it is not [an] observatory, but the official meteorological agency of HK,
 # and also serves as the official timing agency), there are some missing
 # and incorrect rules. Although the exact switch over time is missing, I
-# think 3:30 is correct. The official DST record for Hong Kong can be
-# obtained from
-# http://www.hko.gov.hk/gts/time/Summertime.htm
+# think 3:30 is correct.
 
 # From Phake Nick (2018-10-27):
 # According to Singaporean newspaper
@@ -695,10 +797,10 @@ Zone	Asia/Urumqi	5:50:20	-	LMT	1928
 #   Resolution of the Legislative Council passed on 9 May 1979
 #	https://www.legco.gov.hk/yr78-79/english/lc_sitg/hansard/h790509.pdf#page=39
 
-# From Paul Eggert (2019-05-31):
+# From Paul Eggert (2020-04-15):
 # Here are the dates given at
-# https://www.hko.gov.hk/gts/time/Summertime.htm
-# as of 2014-06-19:
+# https://www.hko.gov.hk/en/gts/time/Summertime.htm
+# as of 2020-02-10:
 # Year        Period
 # 1941        15 Jun to 30 Sep
 # 1942        Whole year
@@ -1828,6 +1930,47 @@ Zone	Asia/Jerusalem	2:20:54 -	LMT	1880
 
 # '9:00' and 'JST' is from Guy Harris.
 
+# From Paul Eggert (2020-01-19):
+# Starting in the 7th century, Japan generally followed an ancient Chinese
+# timekeeping system that divided night and day into six hours each,
+# with hour length depending on season.  In 1873 the government
+# started requiring the use of a Western style 24-hour clock.  See:
+# Yulia Frumer, "Making Time: Astronomical Time Measurement in Tokugawa Japan"
+# <https://www.worldcat.org/oclc/1043907065>.  As the tzdb code and
+# data support only 24-hour clocks, its tables model timestamps before
+# 1873 using Western-style local mean time.
+
+# From Hideyuki Suzuki (1998-11-09):
+# 'Tokyo' usually stands for the former location of Tokyo Astronomical
+# Observatory: 139° 44' 40.90" E (9h 18m 58.727s), 35° 39' 16.0" N.
+# This data is from 'Rika Nenpyou (Chronological Scientific Tables) 1996'
+# edited by National Astronomical Observatory of Japan....
+# JST (Japan Standard Time) has been used since 1888-01-01 00:00 (JST).
+# The law is enacted on 1886-07-07.
+
+# From Hideyuki Suzuki (1998-11-16):
+# The ordinance No. 51 (1886) established "standard time" in Japan,
+# which stands for the time on 135° E.
+# In the ordinance No. 167 (1895), "standard time" was renamed to "central
+# standard time".  And the same ordinance also established "western standard
+# time", which stands for the time on 120° E....  But "western standard
+# time" was abolished in the ordinance No. 529 (1937).  In the ordinance No.
+# 167, there is no mention regarding for what place western standard time is
+# standard....
+#
+# I wrote "ordinance" above, but I don't know how to translate.
+# In Japanese it's "chokurei", which means ordinance from emperor.
+
+# From Yu-Cheng Chuang (2013-07-12):
+# ...the Meiji Emperor announced Ordinance No. 167 of Meiji Year 28 "The clause
+# about standard time" ... The adoption began from Jan 1, 1896.
+# https://ja.wikisource.org/wiki/標準時ニ關スル件_(公布時)
+#
+# ...the Showa Emperor announced Ordinance No. 529 of Showa Year 12 ... which
+# means the whole Japan territory, including later occupations, adopt Japan
+# Central Time (UT+9). The adoption began on Oct 1, 1937.
+# https://ja.wikisource.org/wiki/明治二十八年勅令第百六十七號標準時ニ關スル件中改正ノ件
+
 # From Paul Eggert (1995-03-06):
 # Today's _Asahi Evening News_ (page 4) reports that Japan had
 # daylight saving between 1948 and 1951, but "the system was discontinued
@@ -1876,37 +2019,6 @@ Rule	Japan	1948	1951	-	Sep	Sat>=8	25:00	0	S
 Rule	Japan	1949	only	-	Apr	Sat>=1	24:00	1:00	D
 Rule	Japan	1950	1951	-	May	Sat>=1	24:00	1:00	D
 
-# From Hideyuki Suzuki (1998-11-09):
-# 'Tokyo' usually stands for the former location of Tokyo Astronomical
-# Observatory: 139° 44' 40.90" E (9h 18m 58.727s), 35° 39' 16.0" N.
-# This data is from 'Rika Nenpyou (Chronological Scientific Tables) 1996'
-# edited by National Astronomical Observatory of Japan....
-# JST (Japan Standard Time) has been used since 1888-01-01 00:00 (JST).
-# The law is enacted on 1886-07-07.
-
-# From Hideyuki Suzuki (1998-11-16):
-# The ordinance No. 51 (1886) established "standard time" in Japan,
-# which stands for the time on 135° E.
-# In the ordinance No. 167 (1895), "standard time" was renamed to "central
-# standard time".  And the same ordinance also established "western standard
-# time", which stands for the time on 120° E....  But "western standard
-# time" was abolished in the ordinance No. 529 (1937).  In the ordinance No.
-# 167, there is no mention regarding for what place western standard time is
-# standard....
-#
-# I wrote "ordinance" above, but I don't know how to translate.
-# In Japanese it's "chokurei", which means ordinance from emperor.
-
-# From Yu-Cheng Chuang (2013-07-12):
-# ...the Meiji Emperor announced Ordinance No. 167 of Meiji Year 28 "The clause
-# about standard time" ... The adoption began from Jan 1, 1896.
-# https://ja.wikisource.org/wiki/標準時ニ關スル件_(公布時)
-#
-# ...the Showa Emperor announced Ordinance No. 529 of Showa Year 12 ... which
-# means the whole Japan territory, including later occupations, adopt Japan
-# Central Time (UT+9). The adoption began on Oct 1, 1937.
-# https://ja.wikisource.org/wiki/明治二十八年勅令第百六十七號標準時ニ關スル件中改正ノ件
-
 # Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
 Zone	Asia/Tokyo	9:18:59	-	LMT	1887 Dec 31 15:00u
 			9:00	Japan	J%sT
@@ -3086,22 +3198,9 @@ Zone	Asia/Karachi	4:28:12 -	LMT	1907
 # [T]he Palestinian cabinet decision (Mar 8th 2016) published on
 # http://www.palestinecabinet.gov.ps/WebSite/Upload/Decree/GOV_17/16032016134830.pdf
 # states that summer time will end on Oct 29th at 01:00.
-#
-# From Tim Parenti (2016-10-19):
-# Predict fall transitions on October's last Saturday at 01:00 from now on.
-# This is consistent with the 2016 transition as well as our spring
-# predictions.
-#
-# From Paul Eggert (2016-10-19):
-# It's also consistent with predictions in the following URLs today:
-# https://www.timeanddate.com/time/change/gaza-strip/gaza
-# https://www.timeanddate.com/time/change/west-bank/hebron
 
 # From Sharef Mustafa (2018-03-16):
-# Palestine summer time will start on Mar 24th 2018 by advancing the
-# clock by 60 minutes as per Palestinian cabinet decision published on
-# the official website, though the decree did not specify the exact
-# time of the time shift.
+# Palestine summer time will start on Mar 24th 2018 ...
 # http://www.palestinecabinet.gov.ps/Website/AR/NDecrees/ViewFile.ashx?ID=e7a42ab7-ee23-435a-b9c8-a4f7e81f3817
 
 # From Even Scharning (2019-03-23):
@@ -3111,15 +3210,20 @@ Zone	Asia/Karachi	4:28:12 -	LMT	1907
 # From Sharif Mustafa (2019-03-26):
 # The Palestinian cabinet announced today that the switch to DST will
 # be on Fri Mar 29th 2019 by advancing the clock by 60 minutes.
-# The decree signing date is Mar 12th but it was not published till today.
-# The decree does not specify the exact time of switch.
 # http://palestinecabinet.gov.ps/Website/AR/NDecrees/ViewFile.ashx?ID=e54e9ea1-50ee-4137-84df-0d6c78da259b
 #
 # From Even Scharning (2019-04-10):
 # Our source in Palestine said it happened Friday 29 at 00:00 local time....
+
+# From Sharef Mustafa (2019-10-18):
+# Palestine summer time will end on midnight Oct 26th 2019 ...
+# http://www.palestinecabinet.gov.ps/website/ar/ViewDetails?ID=43948
 #
 # From Paul Eggert (2019-04-10):
 # For now, guess spring-ahead transitions are March's last Friday at 00:00.
+#
+# From Tim Parenti (2016-10-19):
+# Predict fall transitions on October's last Saturday at 01:00 from now on.
 
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 Rule EgyptAsia	1957	only	-	May	10	0:00	1:00	S
diff --git a/tz/backward b/tz/backward
index b4ae3cf..e13ae52 100644
--- a/tz/backward
+++ b/tz/backward
@@ -17,6 +17,7 @@ Link	America/Atikokan	America/Coral_Harbour
 Link	America/Argentina/Cordoba	America/Cordoba
 Link	America/Tijuana		America/Ensenada
 Link	America/Indiana/Indianapolis	America/Fort_Wayne
+Link	America/Nuuk		America/Godthab
 Link	America/Indiana/Indianapolis	America/Indianapolis
 Link	America/Argentina/Jujuy	America/Jujuy
 Link	America/Indiana/Knox	America/Knox_IN
diff --git a/tz/backzone b/tz/backzone
index 3ccadd1..91fa21d 100644
--- a/tz/backzone
+++ b/tz/backzone
@@ -33,6 +33,35 @@
 # assumes rules from other files.  In the tz distribution, use
 # 'make PACKRATDATA=backzone zones' to compile and install this file.
 
+
+# From Paul Eggert (2020-04-15):
+# The following remarks should be incorporated into this table sometime.
+# Patches in 'git format-patch' format would be welcome.
+#
+# From Phake Nick (2020-04-15):
+# ... the historical timezone data for those China zones seems to be
+# incorrect.  The transition to GMT+8 date given there for these zones
+# were 1980 which also contradict the file description that they do
+# not disagree with normal zone after 1970.  According to sources that
+# have also been cited in the asia file, except Xinjiang and Tibet,
+# they should have adopted the Beijing Time from around 1949/1950
+# depends on exactly when each of those cities were taken over by the
+# communist army.  And they should also follow the DST setting of
+# Asia/Shanghai after that point of time.  In addition,
+# http://gaz.ncl.edu.tw/detail.jsp?sysid=E1091792 the document from
+# Chongqing Nationalist government say in year 1945 all of China
+# should adopt summer time due to the war (not sure whether it
+# continued after WWII ends)(Probably only enforced in area under
+# their rule at the time?)  The Asia/Harbin's 1932 and 1940 entry
+# should also be incorrect.  As per sources recorded at
+# https://wiki.suikawiki.org/n/%E6%BA%80%E5%B7%9E%E5%9B%BD%E3%81%AE%E6%A8%99%E6%BA%96%E6%99%82
+# , in 1932 Harbin should have adopted UTC+8:00 instead of data
+# currently listed in the tz database according to official
+# announcement from Manchuko.  And they should have adopted GMT+9 in
+# 1937 January 1st according to official announcement at the time
+# being cited on the webpage.
+
+
 # Zones are sorted by zone name.  Each zone is preceded by the
 # name of the country that the zone is in, along with any other
 # commentary and rules associated with the entry.
diff --git a/tz/europe b/tz/europe
index 361b396..5593c60 100644
--- a/tz/europe
+++ b/tz/europe
@@ -549,12 +549,13 @@ Zone	Europe/Dublin	-0:25:00 -	LMT	1880 Aug  2
 			 0:00	1:00	IST	1947 Nov  2  2:00s
 			 0:00	-	GMT	1948 Apr 18  2:00s
 			 0:00	GB-Eire	GMT/IST	1968 Oct 27
-# The next line is for when negative SAVE values are used.
+# Vanguard section, for zic and other parsers that support negative DST.
 			 1:00	Eire	IST/GMT
-# These three lines are for when SAVE values are always nonnegative.
+# Rearguard section, for parsers lacking negative DST; see ziguard.awk.
 #			 1:00	-	IST	1971 Oct 31  2:00u
 #			 0:00	GB-Eire	GMT/IST	1996
 #			 0:00	EU	GMT/IST
+# End of rearguard section.
 
 
 ###############################################################################
@@ -1018,7 +1019,7 @@ Zone	Europe/Prague	0:57:44 -	LMT	1850
 			1:00	Czech	CE%sT	1946 Dec  1  3:00
 # Vanguard section, for zic and other parsers that support negative DST.
 			1:00	-1:00	GMT	1947 Feb 23  2:00
-# Rearguard section, for parsers that do not support negative DST.
+# Rearguard section, for parsers lacking negative DST; see ziguard.awk.
 #			0:00	-	GMT	1947 Feb 23  2:00
 # End of rearguard section.
 			1:00	Czech	CE%sT	1979
@@ -1175,14 +1176,17 @@ Zone America/Danmarkshavn -1:14:40 -	LMT	1916 Jul 28
 			-3:00	-	-03	1980 Apr  6  2:00
 			-3:00	EU	-03/-02	1996
 			0:00	-	GMT
+#
+# Use the old name Scoresbysund, as the current name Ittoqqortoormiit
+# exceeds tzdb's 14-letter limit and has no common English abbreviation.
 Zone America/Scoresbysund -1:27:52 -	LMT	1916 Jul 28 # Ittoqqortoormiit
 			-2:00	-	-02	1980 Apr  6  2:00
 			-2:00	C-Eur	-02/-01	1981 Mar 29
 			-1:00	EU	-01/+00
-Zone America/Godthab	-3:26:56 -	LMT	1916 Jul 28 # Nuuk
+Zone America/Nuuk	-3:26:56 -	LMT	1916 Jul 28 # Godthåb
 			-3:00	-	-03	1980 Apr  6  2:00
 			-3:00	EU	-03/-02
-Zone America/Thule	-4:35:08 -	LMT	1916 Jul 28 # Pituffik air base
+Zone America/Thule	-4:35:08 -	LMT	1916 Jul 28 # Pituffik
 			-4:00	Thule	A%sT
 
 # Estonia
@@ -1552,7 +1556,7 @@ Zone	Europe/Budapest	1:16:20 -	LMT	1890 Oct
 #
 # From January 1st, 1908 the whole of Iceland was standardised at 1 hour
 # behind GMT. Previously, local mean solar time was used in different parts
-# of Iceland, the almanak had been based on Reykjavik mean solar time which
+# of Iceland, the almanak had been based on Reykjavík mean solar time which
 # was 1 hour and 28 minutes behind GMT.
 #
 # "first day of winter" referred to [below] means the first day of the 26 weeks
diff --git a/tz/leap-seconds.list b/tz/leap-seconds.list
index a1bc5a7..ac153da 100644
--- a/tz/leap-seconds.list
+++ b/tz/leap-seconds.list
@@ -62,7 +62,7 @@
 #		Terry Quinn, "The BIPM and the Accurate Measurement
 #		of Time," Proc. of the IEEE, Vol. 79, pp. 894-905,
 #		July, 1991. <http://dx.doi.org/10.1109/5.84965>
-#		reprinted in: 
+#		reprinted in:
 #		   Christine Hackman and Donald B Sullivan (eds.)
 #		   Time and Frequency Measurement
 #		   American Association of Physics Teachers (1996)
@@ -204,10 +204,10 @@
 #	current -- the update time stamp, the data and the name of the file
 #	will not change.
 #
-#	Updated through IERS Bulletin C58
-#	File expires on:  28 June 2020
+#	Updated through IERS Bulletin C59
+#	File expires on:  28 December 2020
 #
-#@	3802291200 
+#@	3818102400
 #
 2272060800	10	# 1 Jan 1972
 2287785600	11	# 1 Jul 1972
@@ -252,4 +252,4 @@
 #	the hash line is also ignored in the
 #	computation.
 #
-#h 	f28827d2 f263b6c3 ec0f19eb a3e0dbf0 97f3fa30
+#h	a1c168ae 27c79a7d 9dddcfc3 bcfe616b 2e2c44ea
diff --git a/tz/leapseconds.awk b/tz/leapseconds.awk
index 1fe5012..924ade9 100755
--- a/tz/leapseconds.awk
+++ b/tz/leapseconds.awk
@@ -68,12 +68,12 @@ BEGIN {
   monthabbr[11] = "Nov"
   monthabbr[12] = "Dec"
 
-  # Strip trailing CR, in case the input has CRLF form a la NIST.
-  RS = "\r?\n"
-
   sstamp_init()
 }
 
+# In case the input has CRLF form a la NIST.
+{ sub(/\r$/, "") }
+
 /^#[ \t]*[Uu]pdated through/ || /^#[ \t]*[Ff]ile expires on/ {
     last_lines = last_lines $0 "\n"
 }
@@ -100,6 +100,17 @@ BEGIN {
 }
 
 END {
+    sstamp_to_ymdhMs(expires, ss_NTP)
+
+    print ""
+    print "# UTC timestamp when this leap second list expires."
+    print "# Any additional leap seconds will come after this."
+    print "# This Expires line is commented out for now,"
+    print "# so that pre-2020a zic implementations do not reject this file."
+    printf "%sExpires %.4d\t%s\t%.2d\t%.2d:%.2d:%.2d\n", \
+      EXPIRES_LINE ? "" : "#", \
+      ss_year, monthabbr[ss_month], ss_mday, ss_hour, ss_min, ss_sec
+
     # The difference between the NTP and POSIX epochs is 70 years
     # (including 17 leap days), each 24 hours of 60 minutes of 60
     # seconds each.
diff --git a/tz/localtime.c b/tz/localtime.c
index 033e88f..6623eac 100644
--- a/tz/localtime.c
+++ b/tz/localtime.c
@@ -158,6 +158,7 @@ static struct tm *gmtsub(struct state const *, time_t const *, int_fast32_t,
 			 struct tm *);
 static bool increment_overflow(int *, int);
 static bool increment_overflow_time(time_t *, int_fast32_t);
+static int_fast64_t leapcorr(struct state const *, time_t);
 static bool normalize_overflow32(int_fast32_t *, int *, int);
 static struct tm *timesub(time_t const *, int_fast32_t, struct state const *,
 			  struct tm *);
@@ -193,20 +194,18 @@ static int		lcl_is_set;
 
 static struct tm	tm;
 
-#if !HAVE_POSIX_DECLS || TZ_TIME_T
-# if HAVE_TZNAME
+#if 2 <= HAVE_TZNAME + TZ_TIME_T
 char *			tzname[2] = {
 	(char *) wildabbr,
 	(char *) wildabbr
 };
-# endif
-# if USG_COMPAT
+#endif
+#if 2 <= USG_COMPAT + TZ_TIME_T
 long			timezone;
 int			daylight;
-# endif
-# ifdef ALTZONE
+#endif
+#if 2 <= ALTZONE + TZ_TIME_T
 long			altzone;
-# endif
 #endif
 
 /* Initialize *S to a value based on UTOFF, ISDST, and DESIGIDX.  */
@@ -276,7 +275,7 @@ update_tzname_etc(struct state const *sp, struct ttinfo const *ttisp)
   if (!ttisp->tt_isdst)
     timezone = - ttisp->tt_utoff;
 #endif
-#ifdef ALTZONE
+#if ALTZONE
   if (ttisp->tt_isdst)
     altzone = - ttisp->tt_utoff;
 #endif
@@ -295,9 +294,9 @@ settzname(void)
 	daylight = 0;
 	timezone = 0;
 #endif
-#ifdef ALTZONE
+#if ALTZONE
 	altzone = 0;
-#endif /* defined ALTZONE */
+#endif
 	if (sp == NULL) {
 		return;
 	}
@@ -643,11 +642,13 @@ tzloadbody(char const *name, struct state *sp, bool doextend,
 
 			    for (i = 0; i < ts->timecnt; i++)
 			      if (sp->timecnt == 0
-				  || sp->ats[sp->timecnt - 1] < ts->ats[i])
+				  || (sp->ats[sp->timecnt - 1]
+				      < ts->ats[i] + leapcorr(sp, ts->ats[i])))
 				break;
 			    while (i < ts->timecnt
 				   && sp->timecnt < TZ_MAX_TIMES) {
-			      sp->ats[sp->timecnt] = ts->ats[i];
+			      sp->ats[sp->timecnt]
+				= ts->ats[i] + leapcorr(sp, ts->ats[i]);
 			      sp->types[sp->timecnt] = (sp->typecnt
 							+ ts->types[i]);
 			      sp->timecnt++;
@@ -2241,20 +2242,6 @@ timeoff(struct tm *tmp, long offset)
 
 #endif /* defined STD_INSPIRED */
 
-/*
-** XXX--is the below the right way to conditionalize??
-*/
-
-#ifdef STD_INSPIRED
-
-/*
-** IEEE Std 1003.1 (POSIX) says that 536457599
-** shall correspond to "Wed Dec 31 23:59:59 UTC 1986", which
-** is not the case if we are accounting for leap seconds.
-** So, we provide the following conversion routines for use
-** when exchanging timestamps with POSIX conforming systems.
-*/
-
 static int_fast64_t
 leapcorr(struct state const *sp, time_t t)
 {
@@ -2270,6 +2257,20 @@ leapcorr(struct state const *sp, time_t t)
 	return 0;
 }
 
+/*
+** XXX--is the below the right way to conditionalize??
+*/
+
+#ifdef STD_INSPIRED
+
+/*
+** IEEE Std 1003.1 (POSIX) says that 536457599
+** shall correspond to "Wed Dec 31 23:59:59 UTC 1986", which
+** is not the case if we are accounting for leap seconds.
+** So, we provide the following conversion routines for use
+** when exchanging timestamps with POSIX conforming systems.
+*/
+
 NETBSD_INSPIRED_EXTERN time_t
 time2posix_z(struct state *sp, time_t t)
 {
@@ -2345,7 +2346,7 @@ posix2time(time_t t)
 #  define daylight 0
 #  define timezone 0
 # endif
-# ifndef ALTZONE
+# if !ALTZONE
 #  define altzone 0
 # endif
 
diff --git a/tz/northamerica b/tz/northamerica
index 8771d96..febf05b 100644
--- a/tz/northamerica
+++ b/tz/northamerica
@@ -86,7 +86,7 @@
 # For more about the first ten years of DST in the United States, see
 # Robert Garland, Ten years of daylight saving from the Pittsburgh standpoint
 # (Carnegie Library of Pittsburgh, 1927).
-# http://www.clpgh.org/exhibit/dst.html
+# https://web.archive.org/web/20160517155308/http://www.clpgh.org/exhibit/dst.html
 #
 # Shanks says that DST was called "War Time" in the US in 1918 and 1919.
 # However, DST was imposed by the Standard Time Act of 1918, which
@@ -1470,7 +1470,8 @@ Zone America/Goose_Bay	-4:01:40 -	LMT	1884 # Happy Valley-Goose Bay
 			-4:00	Canada	A%sT
 
 
-# west Labrador, Nova Scotia, Prince Edward I
+# west Labrador, Nova Scotia, Prince Edward I,
+# Îles-de-la-Madeleine, Listuguj reserve
 
 # From Brian Inglis (2015-07-20):
 # From the historical weather station records available at:
@@ -1489,6 +1490,13 @@ Zone America/Goose_Bay	-4:01:40 -	LMT	1884 # Happy Valley-Goose Bay
 # in Canada to observe DST in 1971 but not 1970; for now we'll assume
 # this is a typo.
 
+# From Jeffery Nichols (2020-01-09):
+# America/Halifax ... also applies to Îles-de-la-Madeleine and the Listuguj
+# reserve in Quebec. Officially, this came into effect on January 1, 2007
+# (Legal Time Act, CQLR c T-5.1), but the legislative debates surrounding that
+# bill say that it is "accommodating the customs and practices" of those
+# regions, which suggests that they have always been in-line with Halifax.
+
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 Rule	Halifax	1916	only	-	Apr	 1	0:00	1:00	D
 Rule	Halifax	1916	only	-	Oct	 1	0:00	0	S
@@ -1582,19 +1590,20 @@ Zone America/Moncton	-4:19:08 -	LMT	1883 Dec  9
 
 # Quebec
 
-# From Paul Eggert (2015-03-24):
+# From Paul Eggert (2020-01-10):
 # See America/Toronto for most of Quebec, including Montreal.
+# See America/Halifax for the Îles de la Madeleine and the Listuguj reserve.
 #
 # Matthews and Vincent (1998) also write that Quebec east of the -63
 # meridian is supposed to observe AST, but residents as far east as
 # Natashquan use EST/EDT, and residents east of Natashquan use AST.
 # The Quebec department of justice writes in
 # "The situation in Minganie and Basse-Côte-Nord"
-# http://www.justice.gouv.qc.ca/english/publications/generale/temps-minganie-a.htm
+# https://www.justice.gouv.qc.ca/en/department/ministre/functions-and-responsabilities/legal-time-in-quebec/the-situation-in-minganie-and-basse-cote-nord/
 # that the coastal strip from just east of Natashquan to Blanc-Sablon
 # observes Atlantic standard time all year round.
-# https://www.assnat.qc.ca/Media/Process.aspx?MediaId=ANQ.Vigie.Bll.DocumentGenerique_8845en
-# says this common practice was codified into law as of 2007.
+# This common practice was codified into law as of 2007; see Legal Time Act,
+# CQLR c T-5.1 <http://legisquebec.gouv.qc.ca/en/ShowDoc/cs/T-5.1>.
 # For lack of better info, guess this practice began around 1970, contra to
 # Shanks & Pottenger who have this region observing AST/ADT.
 
@@ -1613,6 +1622,15 @@ Zone America/Blanc-Sablon -3:48:28 -	LMT	1884
 # Nipigon (EST) and Rainy River (CST) are the largest that we know of.
 # Far west Ontario is like Winnipeg; far east Quebec is like Halifax.
 
+# From Jeffery Nichols (2020-02-06):
+# According to the [Shanks] atlas, those western Ontario zones are huge,
+# covering most of Ontario northwest of Sault Ste Marie and Timmins.
+# The zones seem to include towns bigger than the ones they're named after,
+# like Dryden in America/Rainy_River and Wawa (and maybe Attawapiskat) in
+# America/Nipigon.  I assume it's too much trouble to change the name of the
+# zone (like when you found out that America/Glace_Bay includes Sydney, Nova
+# Scotia)....
+
 # From Mark Brader (2003-07-26):
 # [According to the Toronto Star] Orillia, Ontario, adopted DST
 # effective Saturday, 1912-06-22, 22:00; the article mentions that
@@ -2419,6 +2437,18 @@ Zone America/Creston	-7:46:04 -	LMT	1884
 # obtained in November 2008 should be ignored...
 # I apologize for reporting incorrect information in 2008.
 
+# From Tim Parenti (2020-03-05):
+# The government of Yukon announced [yesterday] the cessation of seasonal time
+# changes.  "After clocks are pushed ahead one hour on March 8, the territory
+# will remain on [UTC-07].  ... [The government] found 93 per cent of
+# respondents wanted to end seasonal time changes and, of that group, 70 per
+# cent wanted 'permanent Pacific Daylight Saving Time.'"
+# https://www.cbc.ca/news/canada/north/yukon-end-daylight-saving-time-1.5486358
+#
+# Although the government press release prefers PDT, we prefer MST for
+# consistency with nearby Dawson Creek, Creston, and Fort Nelson.
+# https://yukon.ca/en/news/yukon-end-seasonal-time-change
+
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
 Rule	NT_YK	1918	only	-	Apr	14	2:00	1:00	D
 Rule	NT_YK	1918	only	-	Oct	27	2:00	0	S
@@ -2473,11 +2503,13 @@ Zone America/Inuvik	0	-	-00	1953 # Inuvik founded
 Zone America/Whitehorse	-9:00:12 -	LMT	1900 Aug 20
 			-9:00	NT_YK	Y%sT	1967 May 28  0:00
 			-8:00	NT_YK	P%sT	1980
-			-8:00	Canada	P%sT
+			-8:00	Canada	P%sT	2020 Mar  8  2:00
+			-7:00	-	MST
 Zone America/Dawson	-9:17:40 -	LMT	1900 Aug 20
 			-9:00	NT_YK	Y%sT	1973 Oct 28  0:00
 			-8:00	NT_YK	P%sT	1980
-			-8:00	Canada	P%sT
+			-8:00	Canada	P%sT	2020 Mar  8  2:00
+			-7:00	-	MST
 
 
 ###############################################################################
diff --git a/tz/private.h b/tz/private.h
index 1ead147..8513663 100644
--- a/tz/private.h
+++ b/tz/private.h
@@ -132,11 +132,16 @@
 ** Nested includes
 */
 
-/* Avoid clashes with NetBSD by renaming NetBSD's declarations.  */
+/* Avoid clashes with NetBSD by renaming NetBSD's declarations.
+   If defining the 'timezone' variable, avoid a clash with FreeBSD's
+   'timezone' function by renaming its declaration.  */
 #define localtime_rz sys_localtime_rz
 #define mktime_z sys_mktime_z
 #define posix2time_z sys_posix2time_z
 #define time2posix_z sys_time2posix_z
+#if defined USG_COMPAT && USG_COMPAT == 2
+# define timezone sys_timezone
+#endif
 #define timezone_t sys_timezone_t
 #define tzalloc sys_tzalloc
 #define tzfree sys_tzfree
@@ -145,6 +150,9 @@
 #undef mktime_z
 #undef posix2time_z
 #undef time2posix_z
+#if defined USG_COMPAT && USG_COMPAT == 2
+# undef timezone
+#endif
 #undef timezone_t
 #undef tzalloc
 #undef tzfree
@@ -198,6 +206,14 @@
 # endif
 #endif
 
+#ifndef ALTZONE
+# if defined __sun || defined _M_XENIX
+#  define ALTZONE 1
+# else
+#  define ALTZONE 0
+# endif
+#endif
+
 #ifndef R_OK
 #define R_OK	4
 #endif /* !defined R_OK */
@@ -409,6 +425,10 @@ static time_t sys_time(time_t *x) { return time(x); }
 
 typedef time_tz tz_time_t;
 
+# undef  asctime
+# define asctime tz_asctime
+# undef  asctime_r
+# define asctime_r tz_asctime_r
 # undef  ctime
 # define ctime tz_ctime
 # undef  ctime_r
@@ -473,11 +493,13 @@ typedef time_tz tz_time_t;
 #  undef  timezone
 #  define timezone tz_timezone
 # endif
-# ifdef ALTZONE
+# if ALTZONE
 #  undef  altzone
 #  define altzone tz_altzone
 # endif
 
+char *asctime(struct tm const *);
+char *asctime_r(struct tm const *restrict, char *restrict);
 char *ctime(time_t const *);
 char *ctime_r(time_t const *, char *);
 double difftime(time_t, time_t) ATTRIBUTE_CONST;
@@ -512,17 +534,14 @@ extern char *asctime_r(struct tm const *restrict, char *restrict);
 extern char **environ;
 #endif
 
-#if TZ_TIME_T || !HAVE_POSIX_DECLS
-# if HAVE_TZNAME
+#if 2 <= HAVE_TZNAME + (TZ_TIME_T || !HAVE_POSIX_DECLS)
 extern char *tzname[];
-# endif
-# if USG_COMPAT
+#endif
+#if 2 <= USG_COMPAT + (TZ_TIME_T || !HAVE_POSIX_DECLS)
 extern long timezone;
 extern int daylight;
-# endif
 #endif
-
-#ifdef ALTZONE
+#if 2 <= ALTZONE + (TZ_TIME_T || !HAVE_POSIX_DECLS)
 extern long altzone;
 #endif
 
diff --git a/tz/strftime.c b/tz/strftime.c
index ac26f4b..14cbc9a 100644
--- a/tz/strftime.c
+++ b/tz/strftime.c
@@ -492,7 +492,7 @@ label:
 				*/
 				continue;
 			case 'z':
-#if defined TM_GMTOFF || USG_COMPAT || defined ALTZONE
+#if defined TM_GMTOFF || USG_COMPAT || ALTZONE
 				{
 				long		diff;
 				char const *	sign;
@@ -529,7 +529,7 @@ label:
 					continue;
 #  endif
 				else
-#  ifdef ALTZONE
+#  if ALTZONE
 					diff = -altzone;
 #  else
 					continue;
diff --git a/tz/theory.html b/tz/theory.html
index 7af7cb2..c0e6f02 100644
--- a/tz/theory.html
+++ b/tz/theory.html
@@ -298,6 +298,10 @@ in decreasing order of importance:
     If a name is changed, put its old spelling in the
     '<code>backward</code>' file.
     This means old spellings will continue to work.
+    Ordinarily a name change should occur only in the rare case when
+    a location's consensus English-language spelling changes; for example,
+    in 2008 <code>Asia/Calcutta</code> was renamed to <code>Asia/Kolkata</code>
+    due to long-time widespread use of the new city name instead of the old.
   </li>
 </ul>
 
@@ -1054,23 +1058,6 @@ an older <code>zic</code>.
     The functions were inspired by <a href="https://netbsd.org/">NetBSD</a>.
   </li>
   <li>
-    A function <code>tzsetwall</code> has been added to arrange for the
-    system's best approximation to local (wall clock) time to be delivered
-    by subsequent calls to <code>localtime</code>.
-    Source code for portable applications that "must" run on local
-    time should call <code>tzsetwall</code>;
-    if such code is moved to "old" systems that do not
-    provide <code>tzsetwall</code>, you will not be able to generate an
-    executable program.
-    (These functions also arrange for local time to
-    be used if <code>tzset</code> is called &ndash; directly or
-    indirectly &ndash; and there is no <code>TZ</code> environment
-    variable; portable applications should not, however, rely on this
-    behavior since it is not the way <a
-    href="https://en.wikipedia.org/wiki/UNIX_System_V#SVR2"><abbr>SVR2</abbr></a>
-    systems behave.)
-  </li>
-  <li>
     Negative <code>time_t</code> values are supported, on systems
     where <code>time_t</code> is signed.
   </li>
@@ -1137,7 +1124,7 @@ The vestigial <abbr>API</abbr>s are:
     may now examine <code>localtime(&amp;clock)-&gt;tm_zone</code>
     (if <code>TM_ZONE</code> is defined) or
     <code>tzname[localtime(&amp;clock)-&gt;tm_isdst]</code>
-    (if <code>HAVE_TZNAME</code> is defined) to learn the correct time
+    (if <code>HAVE_TZNAME</code> is nonzero) to learn the correct time
     zone abbreviation to use.
   </li>
   <li>
diff --git a/tz/tz-art.html b/tz/tz-art.html
index 8c57174..93a99e4 100644
--- a/tz/tz-art.html
+++ b/tz/tz-art.html
@@ -458,6 +458,15 @@ Supernaw.</td></tr>
 <tr><td><a href="https://www.allmusic.com/album/youre-getting-better-the-word-jazz-dot-masters-mw0000736197">AMG Rating</a></td><td>4.5 stars</td></tr>
 <tr><td>Notes</td><td>Includes the piece "What Time Is It"
 ("He knew what time it was everywhere...that counted").</td></tr>
+<tr><td>&nbsp;</td><td></td></tr>
+<tr><td>Artist</td><td>Chicago</td></tr>
+<tr><td>CD</td><td>Chicago Transit Authority</td></tr>
+<tr><td>Copyright Date</td><td>1969</td></tr>
+<tr><td>Label</td><td>Columbia</td></tr>
+<tr><td>ID</td><td>64409</td></tr>
+<tr><td>Total Time</td><td>1:16:20</td></tr>
+<tr><td><a href="https://www.allmusic.com/album/chicago-transit-authority-mw0000189364">AMG Rating</a></td><td>4 stars</td></tr>
+<tr><td>Notes</td><td>Includes the song "Does Anybody Really Know What Time It Is?"</td></tr>
 </table>
 <h2>Comics</h2>
 <ul>
@@ -472,7 +481,8 @@ The webcomic <em>xkcd</em> has the strip
 "<a href='https://xkcd.com/1799/'>Bad Map Projection: Time Zones</a>"
 (2017-02-15),
 "<a href='https://xkcd.com/1883/'>Supervillain Plan</a>" (2017-08-30),
-and "<a href='https://xkcd.com/2050/'>6/6 Time</a>" (2018-09-24).
+"<a href='https://xkcd.com/2050/'>6/6 Time</a>" (2018-09-24),
+and "<a href='https://xkcd.com/2266/'>Leap Smearing</a>" (2020-02-10).
 The related book <em>What If?</em> has an entry
 "<a href='https://what-if.xkcd.com/26/'>Leap Seconds</a>" (2012-12-31).
 </li>
diff --git a/tz/tz-link.html b/tz/tz-link.html
index e34ea20..1f893f6 100644
--- a/tz/tz-link.html
+++ b/tz/tz-link.html
@@ -49,6 +49,7 @@ area.
 	<ul>
 	  <li><a href="#civil">Civil time concepts and history</a></li>
 	  <li><a href="#national">National histories of legal time</a></li>
+	  <li><a href="#costs">Costs and benefits of time shifts</a></li>
 	  <li><a href="#precision">Precision timekeeping</a></li>
 	  <li><a href="#notation">Time notation</a></li>
 	  <li><a href="#see-also">See also</a></li>
@@ -81,11 +82,12 @@ title="Berkeley Software Distribution">BSD</abbr></a>,
 <a href="https://www.openbsd.org">Open<abbr>BSD</abbr></a>,
 <a href="https://www.chromium.org/chromium-os">Chromium OS</a>,
 <a href="https://cygwin.com">Cygwin</a>,
+<a href="https://mariadb.org">MariaDB</a>,
 <a href="https://en.wikipedia.org/wiki/MINIX">MINIX</a>,
 <a href="https://www.mysql.com">MySQL</a>,
 <a href="https://en.wikipedia.org/wiki/WebOS"><abbr
 title="Web Operating System">webOS</abbr></a>,
-<a href="https://ibm.com/aix"><abbr
+<a href="https://en.wikipedia.org/wiki/IBM_AIX"><abbr
 title="Advanced Interactive eXecutive">AIX</abbr></a>,
 <a href="https://en.wikipedia.org/wiki/BlackBerry_10">BlackBerry 10</a>,
 <a href="https://www.apple.com/ios"><abbr
@@ -167,7 +169,8 @@ then <samp>za</samp> through <samp>zz</samp>, then <samp>zza</samp>
 through <samp>zzz</samp>, and so on).
 Since version 2016h, each release has contained a text file named
 "<samp>version</samp>" whose first (and currently only) line is the version.
-The releases are also available in an
+Older releases are <a href="https://ftp.iana.org/tz/releases/">archived</a>,
+and are also available in an
 <a href="ftp://ftp.iana.org/tz/releases/"><abbr
 title="File Transfer Protocol">FTP</abbr> directory</a> via a
 less-secure protocol.</p>
@@ -826,10 +829,10 @@ zones and daylight saving time</a>.</dd>
 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
+<a href="https://www.hko.gov.hk/en/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
+href="https://www.smg.gov.mo/en/subpage/224/page/174">similar
 history for Macau</a>.
 Unfortunately the latter is incomplete and has errors.</dd>
 <dt>Czech Republic</dt>
@@ -865,7 +868,7 @@ href="https://www.dia.govt.nz/Daylight-Saving-History">History of
 Daylight Saving</a>.</dd>
 <dt>Singapore</dt>
 <dd><a id="Singapore"
-href="http://www.math.nus.edu.sg/~mathelmr/teaching/timezone.html">Why
+href="https://web.archive.org/web/20190822231045/http://www.math.nus.edu.sg/~mathelmr/teaching/timezone.html">Why
 is Singapore in the "Wrong" Time Zone?</a> details the
 history of legal time in Singapore and Malaysia.</dd>
 <dt>United Kingdom</dt>
@@ -880,12 +883,46 @@ Time Zone Proceedings</a> lists changes to time zone boundaries.</dd>
 <dt>Uruguay</dt>
 <dd>The Oceanography, Hydrography, and Meteorology Service of the Uruguayan
 Navy (SOHMA) publishes an annual <a
-href="http://www.armada.gub.uy/sohma/index.php/servicios/datos-astronomicos" hreflang="es">almanac
+href="http://sohma.armada.mil.uy/index.php/servicios/datos-astronomicos" hreflang="es">almanac
 (in Spanish)</a>.</dd>
 </dl>
 </section>
 
 <section>
+<h2 id="costs">Costs and benefits of time shifts</h2>
+<p>Various sources argue for and against daylight saving time and time
+zone shifts, and many scientific studies have been conducted. This
+section summarizes reviews of scientific literature in the area.</p>
+<ul>
+<li>Carey RN, Sarma KM.
+<a href="https://bmjopen.bmj.com/content/7/6/e014319.long">Impact of
+daylight saving time on road traffic collision risk: a systematic
+review</a>.
+<em>BMJ Open.</em> 2017;7(6):e014319. doi:<a href="https://doi.org/10.1136/bmjopen-2016-014319">10.1136/bmjopen-2016-014319</a>.
+This reviews research literature and concludes that the evidence
+neither supports nor refutes road safety benefits from
+shifts in time zones.</li>
+<li>Havranek T, Herman D, Irsova D.
+<a href="https://www.econstor.eu/handle/10419/174191">Does daylight
+saving save electricity? A meta-analysis</a>. <em>Energy J.</em>
+2018;39(2).
+doi:<a href="https://doi.org/10.5547/01956574.39.2.thav">10.5547/01956574.39.2.thav</a>.
+This analyzes research literature and concludes, "Electricity savings
+are larger for countries farther away from the equator, while
+subtropical regions consume more electricity because of DST."</li>
+<li>Roenneberg T, Winnebeck EC, Klerman EB.
+<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6692659/">Daylight
+saving time and artificial time zones &ndash; a battle between
+biological and social times</a>. <em>Front Physiol.</em> 2019;10:944.
+doi:<a href="https://doi.org/10.3389/fphys.2019.00944">10.3389/fphys.2019.00944</a>.
+This reviews evidence about the health effects of DST and concludes,
+"In summary, the scientific literature strongly argues against the
+switching between DST and Standard Time and even more so against
+adopting DST permanently."</li>
+</ul>
+</section>
+
+<section>
 <h2 id="precision">Precision timekeeping</h2>
 <ul>
 <li><a
@@ -1022,7 +1059,7 @@ specifies an <abbr>ISO</abbr> 8601
 profile for use in new Internet
 protocols.</li>
 <li>
-<a href="https://www.hackcraft.net/web/datetime/">Date &amp; Time
+<a href="https://web.archive.org/web/20190130042457/https://www.hackcraft.net/web/datetime/">Date &amp; Time
 Formats on the Web</a> surveys web- and Internet-oriented date and time
 formats.</li>
 <li>Alphabetic time zone abbreviations should not be used as unique
diff --git a/tz/tzfile.5 b/tz/tzfile.5
index cd4c483..3f13563 100644
--- a/tz/tzfile.5
+++ b/tz/tzfile.5
@@ -42,6 +42,7 @@ Six four-byte integer values, in the following order:
 .TP
 .I tzh_ttisutcnt
 The number of UT/local indicators stored in the file.
+(UT is Universal Time.)
 .TP
 .I tzh_ttisstdcnt
 The number of standard/wall indicators stored in the file.
diff --git a/tz/zdump.8 b/tz/zdump.8
index fb6b8df..98109ad 100644
--- a/tz/zdump.8
+++ b/tz/zdump.8
@@ -74,11 +74,11 @@ implementations with different time representations.
 Cut off interval output at the given year(s).
 Cutoff times are computed using the proleptic Gregorian calendar with year 0
 and with Universal Time (UT) ignoring leap seconds.
-The lower bound is exclusive and the upper is inclusive; for example, a
-.I loyear
-of 1970 excludes a transition occurring at 1970-01-01 00:00:00 UTC but a
-.I hiyear
-of 1970 includes the transition.
+Cutoffs are at the start of each year, where the lower-bound
+timestamp is exclusive and the upper is inclusive; for example,
+.B "\*-c 1970,2070"
+selects transitions after 1970-01-01 00:00:00 UTC
+and on or before 2070-01-01 00:00:00 UTC.
 The default cutoff is
 .BR \*-500,2500 .
 .TP
diff --git a/tz/zdump.c b/tz/zdump.c
index 0fc8ced..b532fe3 100644
--- a/tz/zdump.c
+++ b/tz/zdump.c
@@ -328,12 +328,12 @@ abbrok(const char *const abbrp, const char *const zone)
 	cp = abbrp;
 	while (is_alpha(*cp) || is_digit(*cp) || *cp == '-' || *cp == '+')
 		++cp;
-	if (cp - abbrp < 3)
+	if (*cp)
+	  wp = _("has characters other than ASCII alphanumerics, '-' or '+'");
+	else if (cp - abbrp < 3)
 	  wp = _("has fewer than 3 characters");
 	else if (cp - abbrp > 6)
 	  wp = _("has more than 6 characters");
-	else if (*cp)
-	  wp = _("has characters other than ASCII alphanumerics, '-' or '+'");
 	else
 	  return;
 	fflush(stdout);
diff --git a/tz/zic.8 b/tz/zic.8
index dc0220f..b57cd2b 100644
--- a/tz/zic.8
+++ b/tz/zic.8
@@ -108,7 +108,7 @@ and it should not be combined with
 .B "\*-b slim"
 if
 .IR timezone 's
-transitions are at standard time or UT instead of local time.
+transitions are at standard time or Universal Time (UT) instead of local time.
 .TP
 .BR "\*-r " "[\fB@\fP\fIlo\fP][\fB/@\fP\fIhi\fP]"
 Reduce the size of output files by limiting their applicability
@@ -606,7 +606,9 @@ However, the behavior is unspecified if multiple zone or link lines
 define the same name, or if the source of one link line is the target
 of another.
 .PP
-Lines in the file that describes leap seconds have the following form:
+The file that describes leap seconds can have leap lines and an
+expiration line.
+Leap lines have the following form:
 .nf
 .ti +.5i
 .ta \w'Leap\0\0'u +\w'YEAR\0\0'u +\w'MONTH\0\0'u +\w'DAY\0\0'u +\w'HH:MM:SS\0\0'u +\w'CORR\0\0'u
@@ -646,6 +648,43 @@ or
 .q "Rolling"
 if the leap second time given by the other fields should be interpreted as
 local (wall clock) time.
+.PP
+The expiration line, if present, has the form:
+.nf
+.ti +.5i
+.ta \w'Expires\0\0'u +\w'YEAR\0\0'u +\w'MONTH\0\0'u +\w'DAY\0\0'u
+.sp
+Expires	YEAR	MONTH	DAY	HH:MM:SS
+.sp
+For example:
+.ti +.5i
+.sp
+Expires	2020	Dec	28	00:00:00
+.sp
+.fi
+The
+.BR YEAR ,
+.BR MONTH ,
+.BR DAY ,
+and
+.B HH:MM:SS
+fields give the expiration timestamp in UTC for the leap second table;
+.B zic
+outputs this expiration timestamp by truncating the end of the output
+file to the timestamp.
+If there is no expiration line,
+.B zic
+also accepts a comment
+.q "#expires \fIE\fP ...\&"
+where
+.I E
+is the expiration timestamp as a decimal integer count of seconds
+since the Epoch, not counting leap seconds.
+However, the
+.q "#expires"
+comment is an obsolescent feature,
+and the leap second file should use an expiration line
+instead of relying on a comment.
 .SH "EXTENDED EXAMPLE"
 Here is an extended example of
 .B zic
diff --git a/tz/zic.c b/tz/zic.c
index a84703a..2875b55 100644
--- a/tz/zic.c
+++ b/tz/zic.c
@@ -153,13 +153,14 @@ extern int	optind;
 
 static void	addtt(zic_t starttime, int type);
 static int	addtype(zic_t, char const *, bool, bool, bool);
-static void	leapadd(zic_t, bool, int, int);
+static void	leapadd(zic_t, int, int);
 static void	adjleap(void);
 static void	associate(void);
 static void	dolink(const char *, const char *, bool);
 static char **	getfields(char * buf);
 static zic_t	gethms(const char * string, const char * errstring);
 static zic_t	getsave(char *, bool *);
+static void	inexpires(char **, int);
 static void	infile(const char * filename);
 static void	inleap(char ** fields, int nfields);
 static void	inlink(char ** fields, int nfields);
@@ -224,6 +225,7 @@ static int		typecnt;
 #define LC_ZONE		1
 #define LC_LINK		2
 #define LC_LEAP		3
+#define LC_EXPIRES	4
 
 /*
 ** Which fields are which on a Zone line.
@@ -289,6 +291,9 @@ static int		typecnt;
 #define LP_ROLL		6
 #define LEAP_FIELDS	7
 
+/* Expires lines are like Leap lines, except without CORR and ROLL fields.  */
+#define EXPIRES_FIELDS	5
+
 /*
 ** Year synonyms.
 */
@@ -332,6 +337,7 @@ static struct lookup const zi_line_codes[] = {
 };
 static struct lookup const leap_line_codes[] = {
 	{ "Leap",	LC_LEAP },
+	{ "Expires",	LC_EXPIRES },
 	{ NULL,		0}
 };
 
@@ -613,6 +619,12 @@ static zic_t const max_time = MAXVAL(zic_t, TIME_T_BITS_IN_FILE);
 static zic_t lo_time = MINVAL(zic_t, TIME_T_BITS_IN_FILE);
 static zic_t hi_time = MAXVAL(zic_t, TIME_T_BITS_IN_FILE);
 
+/* The time specified by an Expires line, or negative if no such line.  */
+static zic_t leapexpires = -1;
+
+/* The time specified by an #expires comment, or negative if no such line.  */
+static zic_t comment_leapexpires = -1;
+
 /* Set the time range of the output to TIMERANGE.
    Return true if successful.  */
 static bool
@@ -1206,7 +1218,8 @@ infile(const char *name)
 			++nfields;
 		}
 		if (nfields == 0) {
-			/* nothing to do */
+		  if (name == leapsec && *buf == '#')
+		    sscanf(buf, "#expires %"SCNdZIC, &comment_leapexpires);
 		} else if (wantcont) {
 			wantcont = inzcont(fields, nfields);
 		} else {
@@ -1231,6 +1244,10 @@ infile(const char *name)
 					inleap(fields, nfields);
 					wantcont = false;
 					break;
+				case LC_EXPIRES:
+					inexpires(fields, nfields);
+					wantcont = false;
+					break;
 				default:	/* "cannot happen" */
 					fprintf(stderr,
 _("%s: panic: Invalid l_value %d\n"),
@@ -1488,8 +1505,8 @@ inzsub(char **fields, int nfields, bool iscont)
 	return hasuntil;
 }
 
-static void
-inleap(char **fields, int nfields)
+static zic_t
+getleapdatetime(char **fields, int nfields, bool expire_line)
 {
 	register const char *		cp;
 	register const struct lookup *	lp;
@@ -1500,10 +1517,6 @@ inleap(char **fields, int nfields)
 	zic_t				t;
 	char xs;
 
-	if (nfields != LEAP_FIELDS) {
-		error(_("wrong number of fields on Leap line"));
-		return;
-	}
 	dayoff = 0;
 	cp = fields[LP_YEAR];
 	if (sscanf(cp, "%"SCNdZIC"%c", &year, &xs) != 1) {
@@ -1511,13 +1524,15 @@ inleap(char **fields, int nfields)
 		** Leapin' Lizards!
 		*/
 		error(_("invalid leaping year"));
-		return;
+		return -1;
 	}
-	if (!leapseen || leapmaxyear < year)
+	if (!expire_line) {
+	    if (!leapseen || leapmaxyear < year)
 		leapmaxyear = year;
-	if (!leapseen || leapminyear > year)
+	    if (!leapseen || leapminyear > year)
 		leapminyear = year;
-	leapseen = true;
+	    leapseen = true;
+	}
 	j = EPOCH_YEAR;
 	while (j != year) {
 		if (year > j) {
@@ -1531,7 +1546,7 @@ inleap(char **fields, int nfields)
 	}
 	if ((lp = byword(fields[LP_MONTH], mon_names)) == NULL) {
 		error(_("invalid month name"));
-		return;
+		return -1;
 	}
 	month = lp->l_value;
 	j = TM_JANUARY;
@@ -1544,47 +1559,60 @@ inleap(char **fields, int nfields)
 	if (sscanf(cp, "%d%c", &day, &xs) != 1 ||
 		day <= 0 || day > len_months[isleap(year)][month]) {
 			error(_("invalid day of month"));
-			return;
+			return -1;
 	}
 	dayoff = oadd(dayoff, day - 1);
 	if (dayoff < min_time / SECSPERDAY) {
 		error(_("time too small"));
-		return;
+		return -1;
 	}
 	if (dayoff > max_time / SECSPERDAY) {
 		error(_("time too large"));
-		return;
+		return -1;
 	}
 	t = dayoff * SECSPERDAY;
 	tod = gethms(fields[LP_TIME], _("invalid time of day"));
-	cp = fields[LP_CORR];
-	{
-		register bool	positive;
-		int		count;
-
-		if (strcmp(cp, "") == 0) { /* infile() turns "-" into "" */
-			positive = false;
-			count = 1;
-		} else if (strcmp(cp, "+") == 0) {
-			positive = true;
-			count = 1;
-		} else {
-			error(_("illegal CORRECTION field on Leap line"));
-			return;
-		}
-		if ((lp = byword(fields[LP_ROLL], leap_types)) == NULL) {
-			error(_(
-				"illegal Rolling/Stationary field on Leap line"
-				));
-			return;
-		}
-		t = tadd(t, tod);
-		if (t < 0) {
-			error(_("leap second precedes Epoch"));
-			return;
-		}
-		leapadd(t, positive, lp->l_value, count);
-	}
+	t = tadd(t, tod);
+	if (t < 0)
+	  error(_("leap second precedes Epoch"));
+	return t;
+}
+
+static void
+inleap(char **fields, int nfields)
+{
+  if (nfields != LEAP_FIELDS)
+    error(_("wrong number of fields on Leap line"));
+  else {
+    zic_t t = getleapdatetime(fields, nfields, false);
+    if (0 <= t) {
+      struct lookup const *lp = byword(fields[LP_ROLL], leap_types);
+      if (!lp)
+	error(_("invalid Rolling/Stationary field on Leap line"));
+      else {
+	int correction = 0;
+	if (!fields[LP_CORR][0]) /* infile() turns "-" into "".  */
+	  correction = -1;
+	else if (strcmp(fields[LP_CORR], "+") == 0)
+	  correction = 1;
+	else
+	  error(_("invalid CORRECTION field on Leap line"));
+	if (correction)
+	  leapadd(t, correction, lp->l_value);
+      }
+    }
+  }
+}
+
+static void
+inexpires(char **fields, int nfields)
+{
+  if (nfields != EXPIRES_FIELDS)
+    error(_("wrong number of fields on Expires line"));
+  else if (0 <= leapexpires)
+    error(_("multiple Expires lines"));
+  else
+    leapexpires = getleapdatetime(fields, nfields, true);
 }
 
 static void
@@ -2969,28 +2997,24 @@ addtype(zic_t utoff, char const *abbr, bool isdst, bool ttisstd, bool ttisut)
 }
 
 static void
-leapadd(zic_t t, bool positive, int rolling, int count)
+leapadd(zic_t t, int correction, int rolling)
 {
-	register int	i, j;
+	register int i;
 
-	if (leapcnt + (positive ? count : 1) > TZ_MAX_LEAPS) {
+	if (TZ_MAX_LEAPS <= leapcnt) {
 		error(_("too many leap seconds"));
 		exit(EXIT_FAILURE);
 	}
 	for (i = 0; i < leapcnt; ++i)
 		if (t <= trans[i])
 			break;
-	do {
-		for (j = leapcnt; j > i; --j) {
-			trans[j] = trans[j - 1];
-			corr[j] = corr[j - 1];
-			roll[j] = roll[j - 1];
-		}
-		trans[i] = t;
-		corr[i] = positive ? 1 : -count;
-		roll[i] = rolling;
-		++leapcnt;
-	} while (positive && --count != 0);
+	memmove(&trans[i + 1], &trans[i], (leapcnt - i) * sizeof *trans);
+	memmove(&corr[i + 1], &corr[i], (leapcnt - i) * sizeof *corr);
+	memmove(&roll[i + 1], &roll[i], (leapcnt - i) * sizeof *roll);
+	trans[i] = t;
+	corr[i] = correction;
+	roll[i] = rolling;
+	++leapcnt;
 }
 
 static void
@@ -3012,6 +3036,22 @@ adjleap(void)
 		trans[i] = tadd(trans[i], last);
 		last = corr[i] += last;
 	}
+
+	if (leapexpires < 0) {
+	  leapexpires = comment_leapexpires;
+	  if (0 <= leapexpires)
+	    warning(_("\"#expires\" is obsolescent; use \"Expires\""));
+	}
+
+	if (0 <= leapexpires) {
+	  leapexpires = oadd(leapexpires, last);
+	  if (! (leapcnt == 0 || (trans[leapcnt - 1] < leapexpires))) {
+	    error(_("last Leap time does not precede Expires time"));
+	    exit(EXIT_FAILURE);
+	  }
+	  if (leapexpires <= hi_time)
+	    hi_time = leapexpires - 1;
+	}
 }
 
 static char *
diff --git a/tz/zone.tab b/tz/zone.tab
index 408fcb2..8d056e3 100644
--- a/tz/zone.tab
+++ b/tz/zone.tab
@@ -131,8 +131,8 @@ CA	+4906-11631	America/Creston	MST - BC (Creston)
 CA	+5946-12014	America/Dawson_Creek	MST - BC (Dawson Cr, Ft St John)
 CA	+5848-12242	America/Fort_Nelson	MST - BC (Ft Nelson)
 CA	+4916-12307	America/Vancouver	Pacific - BC (most areas)
-CA	+6043-13503	America/Whitehorse	Pacific - Yukon (south)
-CA	+6404-13925	America/Dawson	Pacific - Yukon (north)
+CA	+6043-13503	America/Whitehorse	Pacific - Yukon (east)
+CA	+6404-13925	America/Dawson	Pacific - Yukon (west)
 CC	-1210+09655	Indian/Cocos
 CD	-0418+01518	Africa/Kinshasa	Dem. Rep. of Congo (west)
 CD	-1140+02728	Africa/Lubumbashi	Dem. Rep. of Congo (east)
@@ -189,7 +189,7 @@ GF	+0456-05220	America/Cayenne
 GG	+492717-0023210	Europe/Guernsey
 GH	+0533-00013	Africa/Accra
 GI	+3608-00521	Europe/Gibraltar
-GL	+6411-05144	America/Godthab	Greenland (most areas)
+GL	+6411-05144	America/Nuuk	Greenland (most areas)
 GL	+7646-01840	America/Danmarkshavn	National Park (east coast)
 GL	+7029-02158	America/Scoresbysund	Scoresbysund/Ittoqqortoormiit
 GL	+7634-06847	America/Thule	Thule/Pituffik
@@ -335,7 +335,7 @@ RU	+554521+0373704	Europe/Moscow	MSK+00 - Moscow area
 # The obsolescent zone.tab format cannot represent Europe/Simferopol well.
 # Put it in RU section and list as UA.  See "territorial claims" above.
 # Programs should use zone1970.tab instead; see above.
-UA	+4457+03406	Europe/Simferopol	MSK+00 - Crimea
+UA	+4457+03406	Europe/Simferopol	Crimea
 RU	+5836+04939	Europe/Kirov	MSK+00 - Kirov
 RU	+4621+04803	Europe/Astrakhan	MSK+01 - Astrakhan
 RU	+4844+04425	Europe/Volgograd	MSK+01 - Volgograd
@@ -399,8 +399,8 @@ TV	-0831+17913	Pacific/Funafuti
 TW	+2503+12130	Asia/Taipei
 TZ	-0648+03917	Africa/Dar_es_Salaam
 UA	+5026+03031	Europe/Kiev	Ukraine (most areas)
-UA	+4837+02218	Europe/Uzhgorod	Ruthenia
-UA	+4750+03510	Europe/Zaporozhye	Zaporozh'ye/Zaporizhia; Lugansk/Luhansk (east)
+UA	+4837+02218	Europe/Uzhgorod	Transcarpathia
+UA	+4750+03510	Europe/Zaporozhye	Zaporozhye and east Lugansk
 UG	+0019+03225	Africa/Kampala
 UM	+2813-17722	Pacific/Midway	Midway Islands
 UM	+1917+16637	Pacific/Wake	Wake Island
diff --git a/tz/zone1970.tab b/tz/zone1970.tab
index 822ffa1..53ee77e 100644
--- a/tz/zone1970.tab
+++ b/tz/zone1970.tab
@@ -128,8 +128,8 @@ CA	+4906-11631	America/Creston	MST - BC (Creston)
 CA	+5946-12014	America/Dawson_Creek	MST - BC (Dawson Cr, Ft St John)
 CA	+5848-12242	America/Fort_Nelson	MST - BC (Ft Nelson)
 CA	+4916-12307	America/Vancouver	Pacific - BC (most areas)
-CA	+6043-13503	America/Whitehorse	Pacific - Yukon (south)
-CA	+6404-13925	America/Dawson	Pacific - Yukon (north)
+CA	+6043-13503	America/Whitehorse	Pacific - Yukon (east)
+CA	+6404-13925	America/Dawson	Pacific - Yukon (west)
 CC	-1210+09655	Indian/Cocos
 CH,DE,LI	+4723+00832	Europe/Zurich	Swiss time
 CI,BF,GM,GN,ML,MR,SH,SL,SN,TG	+0519-00402	Africa/Abidjan
@@ -173,7 +173,7 @@ GE	+4143+04449	Asia/Tbilisi
 GF	+0456-05220	America/Cayenne
 GH	+0533-00013	Africa/Accra
 GI	+3608-00521	Europe/Gibraltar
-GL	+6411-05144	America/Godthab	Greenland (most areas)
+GL	+6411-05144	America/Nuuk	Greenland (most areas)
 GL	+7646-01840	America/Danmarkshavn	National Park (east coast)
 GL	+7029-02158	America/Scoresbysund	Scoresbysund/Ittoqqortoormiit
 GL	+7634-06847	America/Thule	Thule/Pituffik
@@ -290,7 +290,7 @@ RS,BA,HR,ME,MK,SI	+4450+02030	Europe/Belgrade
 RU	+5443+02030	Europe/Kaliningrad	MSK-01 - Kaliningrad
 RU	+554521+0373704	Europe/Moscow	MSK+00 - Moscow area
 # Mention RU and UA alphabetically.  See "territorial claims" above.
-RU,UA	+4457+03406	Europe/Simferopol	MSK+00 - Crimea
+RU,UA	+4457+03406	Europe/Simferopol	Crimea
 RU	+5836+04939	Europe/Kirov	MSK+00 - Kirov
 RU	+4621+04803	Europe/Astrakhan	MSK+01 - Astrakhan
 RU	+4844+04425	Europe/Volgograd	MSK+01 - Volgograd
@@ -341,8 +341,8 @@ TT,AG,AI,BL,DM,GD,GP,KN,LC,MF,MS,VC,VG,VI	+1039-06131	America/Port_of_Spain
 TV	-0831+17913	Pacific/Funafuti
 TW	+2503+12130	Asia/Taipei
 UA	+5026+03031	Europe/Kiev	Ukraine (most areas)
-UA	+4837+02218	Europe/Uzhgorod	Ruthenia
-UA	+4750+03510	Europe/Zaporozhye	Zaporozh'ye/Zaporizhia; Lugansk/Luhansk (east)
+UA	+4837+02218	Europe/Uzhgorod	Transcarpathia
+UA	+4750+03510	Europe/Zaporozhye	Zaporozhye and east Lugansk
 UM	+1917+16637	Pacific/Wake	Wake Island
 US	+404251-0740023	America/New_York	Eastern (most areas)
 US	+421953-0830245	America/Detroit	Eastern - MI (most areas)