[tz] [PROPOSED PATCH] Fix 1948-1966 transitions for Los Angeles

[Paul Eggert]

These changes came from research I did to check the historical
background behind Assembly Bill 385, which would abolish daylight
saving time in California, and which has passed the CA Senate
Appropriations Committee's suspense file. See: White JB. Bill
letting California end Daylight Saving Time clears key
committee. Sacramento Bee 2016-08-11.
http://www.sacbee.com/news/politics-government/capitol-alert/article95116732.html

* NEWS, northamerica (CA): For America/Los_Angeles, correct
spring-forward transition times from 02:00 to 02:01 in 1948, from
02:00 to 01:00 in 1950-1966.  Correct the fall-back transition
date for early 1949 from 1949-01-01 to 1949-01-16.
---
 NEWS         |  7 +++++++
 northamerica | 35 ++++++++++++++++++++++++++++++++---
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/NEWS b/NEWS
index ba26a49..a8479eb 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,13 @@ Unreleased, experimental changes
     New leap second 2016-12-31 23:59:60 UTC as per IERS Bulletin C 52.
     (Thanks to Tim Parenti.)
 
+  Changes affecting past time stamps
+
+    For America/Los_Angeles, spring-forward transition times have been
+    corrected from 02:00 to 02:01 in 1948, and from 02:00 to 01:00 in
+    1950-1966.  The fall-back transition date for early 1949 has been
+    corrected from 1949-01-01 to 1949-01-16.
+
   Changes affecting code
 
     zic no longer generates binary files containing POSIX TZ-like
diff --git a/northamerica b/northamerica
index 6256f97..c9c2061 100644
--- a/northamerica
+++ b/northamerica
@@ -413,11 +413,40 @@ Zone America/Denver	-6:59:56 -	LMT	1883 Nov 18 12:00:04
 # north of the Salmon River, and the towns of Burgdorf and Warren),
 # Nevada (except West Wendover), Oregon (except the northern 3/4 of
 # Malheur county), and Washington
+
+# From Paul Eggert (2016-08-19):
+# In 1948 California had an electricity shortage.  To save electricity,
+# in early February PG&E changed power frequency from 60 to 59.5 Hz during
+# daylight hours, causing electric clocks to lose six minutes per day.
+# (This did not change legal time, and is not part of the data here.)
+# See: Ross SA. An energy crisis from the past: Northern California in 1948.
+# Working Paper No. 8, Institute of Governmental Studies, UC Berkeley, 1973-11.
+# http://escholarship.org/uc/item/8x22k30c
+#
+# In another measure to save electricity, DST was instituted from 1948-03-14
+# at 02:01 to 1949-01-16 at 02:00, with the governor having the option to move
+# the fallback transition earlier.  See pages 3-4 of:
+# http://clerk.assembly.ca.gov/sites/clerk.assembly.ca.gov/files/archive/Statutes/1948/48Vol1_Chapters.pdf
+# Apparently the governor did not exercise the option.
+#
+# In response:
+#
+#   Governor Warren received a torrent of objecting mail, and it is not too much
+#   to speculate that the objections to Daylight Saving Time were one important
+#   factor in the defeat of the Dewey-Warren Presidential ticket in California.
+#     -- Ross, p 25
+#
+# Despite the controversy, in 1949 California voters approved Proposition 12,
+# which established DST from April's last Sunday at 01:00 until September's
+# last Sunday at 02:00. This was amended by 1962's Proposition 6, which changed
+# the fall-back date to October's last Sunday. See:
+# http://repository.uchastings.edu/cgi/viewcontent.cgi?article=1501&context=ca_ballot_props
+# http://repository.uchastings.edu/cgi/viewcontent.cgi?article=1636&context=ca_ballot_props
 #
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER
-Rule	CA	1948	only	-	Mar	14	2:00	1:00	D
-Rule	CA	1949	only	-	Jan	 1	2:00	0	S
-Rule	CA	1950	1966	-	Apr	lastSun	2:00	1:00	D
+Rule	CA	1948	only	-	Mar	14	2:01	1:00	D
+Rule	CA	1949	only	-	Jan	16	2:00	0	S
+Rule	CA	1950	1966	-	Apr	lastSun	1:00	1:00	D
 Rule	CA	1950	1961	-	Sep	lastSun	2:00	0	S
 Rule	CA	1962	1966	-	Oct	lastSun	2:00	0	S
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-- 
2.7.4