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1948/51 Japan fallbacks were at 25:00

The 1948-1951 fallback transitions in Japan were at 25:00 on
September's second Saturday, not at 24:00.  (Thanks to Phake Nick.)
* NEWS, asia (Japan): Document this, and implement it as best we can.
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eggert committed Sep 27, 2018
1 parent ec5bc6a commit 40ab5979c3226dcd1f52d6012d8ee5fe53ab148b
Showing with 26 additions and 1 deletion.
  1. +5 −0 NEWS
  2. +21 −1 asia
5 NEWS
@@ -33,6 +33,11 @@ Unreleased, experimental changes
observed DST in 1942/79, not 1961/80, and there were several
errors for transition times and dates. (Thanks to P Chan.)

The 1948-1951 fallback transitions in Japan were at 25:00 on
September's second Saturday, not at 24:00. (Thanks to Phake Nick.)
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.

Changes to time zone abbreviations

Use "PST" and "PDT" for Philippine time. (Thanks to Paul Goyette.)
22 asia
@@ -1610,9 +1610,29 @@ Zone Asia/Jerusalem 2:20:54 - LMT 1880
# http://www.shugiin.go.jp/internet/itdb_housei.nsf/html/houritsu/00719500331039.htm
# ... In summary, it is written as follows. From 24:00 on the first Saturday
# in May, until 0:00 on the day after the second Saturday in September.

# From Phake Nick (2018-09-27):
# [T]he webpage authored by National Astronomical Observatory of Japan
# https://eco.mtk.nao.ac.jp/koyomi/wiki/BBFEB9EF2FB2C6BBFEB9EF.html
# ... mentioned that using Showa 23 (year 1948) as example, 13pm of September
# 11 in summer time will equal to 0am of September 12 in standard time.
# It cited a document issued by the Liaison Office which briefly existed
# during the postwar period of Japan, where the detail on implementation
# of the summer time is described in the document.
# https://eco.mtk.nao.ac.jp/koyomi/wiki/BBFEB9EF2FB2C6BBFEB9EFB2C6BBFEB9EFA4CEBCC2BBDCA4CBA4C4A4A4A4C6.pdf
# The text in the document do instruct a fall back to occur at
# September 11, 13pm in summer time, while ordinary citizens can
# change the clock before they sleep.
#
# From Paul Eggert (2018-09-27):
# This instruction is equivalent to "Sat>=8 25:00", so use that. zic treats
# it like "Sun>=9 01:00", which is not quite the same but is the best we can
# do in any POSIX or C platform. The "25:00" assumes zic from 2007 or later,
# which should be safe now.

# Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S
Rule Japan 1948 only - May Sat>=1 24:00 1:00 D
Rule Japan 1948 1951 - Sep Sun>=9 0:00 0 S
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

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