Correct many pre-1989 entries for Korea.

(Thanks to Sanghyuk Jung.)
* asia (ROK): Add entries for 1948-1959 and correct entries
for 1987-1988.
(Asia/Seoul): Correct entries through 1962.
(Asia/Pyongyang): Guess no change since World War II.
* NEWS: Document this.

2 files changed, 63 insertions, 25 deletions

diff --git a/NEWS b/NEWS
index 4e119ec..2485c93 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,16 @@
 News for the tz database
 
+Unreleased, experimental changes
+
+  Changes affecting past time stamps
+
+    Many pre-1989 time stamps have been corrected for Asia/Seoul and
+    Asia/Pyongyang, based on sources for the Korean-language Wikipedia
+    entry for time in Korea.  (Thanks to Sanghyuk Jung.)  Also, no
+    longer guess that Pyongyang mimicked Seoul time after World War II,
+    as this is politically implausible.
+
+
 Release 2014i - 2014-10-21 22:04:57 -0700
 
   Changes affecting future time stamps
diff --git a/asia b/asia
index 37b2c88..217e8ee 100644
--- a/asia
+++ b/asia
@@ -1663,44 +1663,71 @@ Zone	Asia/Bishkek	4:58:24 -	LMT	1924 May  2
 # Korea (North and South)
 
 # From Annie I. Bang (2006-07-10):
-# http://www.koreaherald.co.kr/SITE/data/html_dir/2006/07/10/200607100012.asp
-# The Ministry of Commerce, Industry and Energy has already
-# commissioned a research project [to reintroduce DST] and has said
-# the system may begin as early as 2008....  Korea ran a daylight
-# saving program from 1949-61 but stopped it during the 1950-53 Korean War.
+# http://www.koreaherald.com/view.php?ud=200607100012
+# Korea ran a daylight saving program from 1949-61 but stopped it
+# during the 1950-53 Korean War.  The system was temporarily enforced
+# between 1987 and 1988 ...
+
+# From Sanghyuk Jung (2014-10-29):
+# http://mm.icann.org/pipermail/tz/2014-October/021830.html
+# According to the Korean Wikipedia
+# http://ko.wikipedia.org/wiki/한국_표준시
+# [oldid=12896437 2014-09-04 08:03 UTC]
+# DST in Republic of Korea was as follows....  And I checked old
+# newspapers in Korean, all articles correspond with data in Wikipedia.
+# For example, the article in 1948 (Korean Language) proved that DST
+# started at June 1 in that year.  For another example, the article in
+# 1988 said that DST started at 2:00 AM in that year.
 
-# From Shanks & Pottenger:
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
-Rule	ROK	1960	only	-	May	15	0:00	1:00	D
-Rule	ROK	1960	only	-	Sep	13	0:00	0	S
-Rule	ROK	1987	1988	-	May	Sun>=8	0:00	1:00	D
-Rule	ROK	1987	1988	-	Oct	Sun>=8	0:00	0	S
-
-# From Paul Eggert (2014-07-01):
-# The following entries are from Shanks & Pottenger, except that I
-# guessed that time zone abbreviations through 1945 followed the same
+Rule	ROK	1948	only	-	Jun	 1	0:00	1:00	D
+Rule	ROK	1948	only	-	Sep	13	0:00	0	S
+Rule	ROK	1949	only	-	Apr	 3	0:00	1:00	D
+Rule	ROK	1949	1951	-	Sep	Sun>=8	0:00	0	S
+Rule	ROK	1950	only	-	Apr	 1	0:00	1:00	D
+Rule	ROK	1951	only	-	May	 6	0:00	1:00	D
+Rule	ROK	1955	only	-	May	 5	0:00	1:00	D
+Rule	ROK	1955	only	-	Sep	 9	0:00	0	S
+Rule	ROK	1956	only	-	May	20	0:00	1:00	D
+Rule	ROK	1956	only	-	Sep	30	0:00	0	S
+Rule	ROK	1957	1960	-	May	Sun>=1	0:00	1:00	D
+Rule	ROK	1957	1960	-	Sep	Sun>=18	0:00	0	S
+Rule	ROK	1987	1988	-	May	Sun>=8	2:00	1:00	D
+Rule	ROK	1987	1988	-	Oct	Sun>=8	3:00	0	S
+
+# From Paul Eggert (2014-10-30):
+# The Korean Wikipedia entry gives the following sources for UT offsets:
+#
+# 1908: Official Journal Article No. 3994 (Edict No. 5)
+# 1912: Governor-General of Korea Official Gazette Issue No. 367
+#       (Announcement No. 338)
+# 1954: Presidential Decree No. 876 (1954-03-17)
+# 1961: Law No. 676 (1961-08-07)
+# 1987: Law No. 3919 (1986-12-31)
+#
+# The Wikipedia entry also has confusing information about a change
+# to UT+9 in April 1910, but then what would be the point of the later change
+# to UT+9 on 1912-01-01?  Omit the 1910 change for now.
+#
+# I guessed that time zone abbreviations through 1945 followed the same
 # rules as discussed under Taiwan, with nominal switches from JST to KST
 # when the respective cities were taken over by the Allies after WWII.
+#
+# For Pyongyang we have no information; guess no changes since World War II.
 
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Asia/Seoul	8:27:52	-	LMT	1890
-			8:30	-	KST	1904 Dec
-			9:00	-	JCST	1928
-			8:30	-	KST	1932
+Zone	Asia/Seoul	8:27:52	-	LMT	1908 Apr  1
+			8:30	-	KST	1912 Jan  1
 			9:00	-	JCST	1937 Oct  1
 			9:00	-	JST	1945 Sep  8
 			9:00	-	KST	1954 Mar 21
-			8:00	ROK	K%sT	1961 Aug 10
+			8:30	ROK	K%sT	1961 Aug 10
 			8:30	-	KST	1968 Oct
 			9:00	ROK	K%sT
-Zone	Asia/Pyongyang	8:23:00 -	LMT	1890
-			8:30	-	KST	1904 Dec
-			9:00	-	JCST	1928
-			8:30	-	KST	1932
+Zone	Asia/Pyongyang	8:23:00 -	LMT	1908 Apr  1
+			8:30	-	KST	1912 Jan  1
 			9:00	-	JCST	1937 Oct  1
 			9:00	-	JST	1945 Aug 24
-			9:00	-	KST	1954 Mar 21
-			8:00	-	KST	1961 Aug 10
 			9:00	-	KST
 
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