[tz] [PATCH] Fix Asia/Shanghai 1940/9 DST transitions

[Paul Eggert]

* NEWS: Mention this.
* asia (Shang): Switch to data from 2014 Li Yu paper.
---
 NEWS |  3 +++
 asia | 34 +++++++++++++++++++++++++++-------
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/NEWS b/NEWS
index a24d4b3..e217a50 100644
--- a/NEWS
+++ b/NEWS
@@ -42,6 +42,9 @@ Unreleased, experimental changes
     zic turns this into 01:00 on the day after September's second
     Saturday, which is the best that POSIX or C platforms can do.
 
+    Incorporate 1940-1949 Asia/Shanghai DST transitions from a 2014
+    paper by Li Yu, replacing more-questionable data from Shanks.
+
   Changes to time zone abbreviations
 
     Use "PST" and "PDT" for Philippine time.  (Thanks to Paul Goyette.)
diff --git a/asia b/asia
index 365593a..a7b5c75 100644
--- a/asia
+++ b/asia
@@ -286,6 +286,29 @@ Zone	Asia/Yangon	6:24:47 -	LMT	1880        # or Rangoon
 
 # China
 
+# From Paul Eggert (2018-10-02):
+# The following comes from Table 1 of:
+# Li Yu. Research on the daylight saving movement in 1940s Shanghai.
+# Nanjing Journal of Social Sciences. 2014;(2):144-50.
+# http://oversea.cnki.net/kns55/detail.aspx?dbname=CJFD2014&filename=NJSH201402020
+# 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 27, when the Communists took power.
+#
+# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
+Rule	Shang	1940	only	-	Jun	 1	 0:00	1:00	D
+Rule	Shang	1940	only	-	Oct	12	24:00	0	S
+Rule	Shang	1941	only	-	Mar	15	 0:00	1:00	D
+Rule	Shang	1941	only	-	Nov	 1	24:00	0	S
+Rule	Shang	1942	only	-	Jan	31	 0:00	1:00	D
+Rule	Shang	1945	only	-	Sep	 1	24:00	0	S
+Rule	Shang	1946	only	-	May	15	 0:00	1:00	D
+Rule	Shang	1946	only	-	Sep	30	24:00	0	S
+Rule	Shang	1947	only	-	Apr	15	 0:00	1:00	D
+Rule	Shang	1947	only	-	Oct	31	24:00	0	S
+Rule	Shang	1948	1949	-	May	 1	 0:00	1:00	D
+Rule	Shang	1948	1949	-	Sep	30	24:00	0	S
+
 # From Guy Harris:
 # People's Republic of China.  Yes, they really have only one time zone.
 
@@ -336,12 +359,9 @@ Zone	Asia/Yangon	6:24:47 -	LMT	1880        # or Rangoon
 # http://data.people.com.cn/pic/101p/1988/04/1988041201.jpg
 
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
-Rule	Shang	1940	only	-	Jun	 3	0:00	1:00	D
-Rule	Shang	1940	1941	-	Oct	 1	0:00	0	S
-Rule	Shang	1941	only	-	Mar	16	0:00	1:00	D
-Rule	PRC	1986	only	-	May	 4	2:00	1:00	D
-Rule	PRC	1986	1991	-	Sep	Sun>=11	2:00	0	S
-Rule	PRC	1987	1991	-	Apr	Sun>=11	2:00	1:00	D
+Rule	PRC	1986	only	-	May	 4	 2:00	1:00	D
+Rule	PRC	1986	1991	-	Sep	Sun>=11	 2:00	0	S
+Rule	PRC	1987	1991	-	Apr	Sun>=11	 2:00	1:00	D
 
 # From Anthony Fok (2001-12-20):
 # BTW, I did some research on-line and found some info regarding these five
@@ -543,7 +563,7 @@ Rule	PRC	1987	1991	-	Apr	Sun>=11	2:00	1:00	D
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 # Beijing time, used throughout China; represented by Shanghai.
 Zone	Asia/Shanghai	8:05:43	-	LMT	1901
-			8:00	Shang	C%sT	1949
+			8:00	Shang	C%sT	1949 May 27
 			8:00	PRC	C%sT
 # Xinjiang time, used by many in western China; represented by Ürümqi / Ürümchi
 # / Wulumuqi.  (Please use Asia/Shanghai if you prefer Beijing time.)
-- 
2.17.1