78 lines
3.1 KiB
Diff
78 lines
3.1 KiB
Diff
From b804a741d5cdb5d1b761de9ad053ba916fa08636 Mon Sep 17 00:00:00 2001
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From: Paul Eggert <eggert@cs.ucla.edu>
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Date: Tue, 22 Dec 2020 15:11:11 -0800
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Subject: [PATCH] Improve doc of zic coalescing zone+DST transitions
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* zic.8: Improve documentation for how certain transitions
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are coalesced. Also, use current data for America/Menominee
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instead an America/Grand_Turk entry that not in current data.
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Improvements suggested by Tim Parenti.
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---
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zic.8 | 36 +++++++++++++++++++++---------------
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1 file changed, 21 insertions(+), 15 deletions(-)
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diff --git a/zic.8 b/zic.8
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index 2273dad..60262d7 100644
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--- a/zic.8
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+++ b/zic.8
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@@ -590,35 +590,41 @@ first transition into standard time.
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In a single zone it is an error if two rules take effect at the same
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instant, or if two zone changes take effect at the same instant.
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.PP
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-If a continuation line subtracts from the UT offset after a transition that
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-would be interpreted to be later if using the continuation line's rules, the
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+If a continuation line subtracts
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+.I N
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+seconds from the UT offset after a transition that would be
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+interpreted to be later if using the continuation line's UT offset and
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+rules, the
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.q "until"
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-time of the earlier zone or continuation line is interpreted according
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-to the continuation line's rules.
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+time of the previous zone or continuation line is interpreted
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+according to the continuation line's UT offset and rules, and any rule
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+that would otherwise take effect in the next
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+.I N
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+seconds is instead assumed to take effect simultaneously.
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For example:
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.br
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.ne 7
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.nf
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.in +2m
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-.ta \w'# Rule\0\0'u +\w'NAME\0\0'u +\w'FROM\0\0'u +\w'max\0\0'u +\w'\*-\0\0'u +\w'Mar\0\0'u +\w'Sun>=8\0\0'u +\w'2:00\0\0'u +\w'SAVE\0\0'u
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+.ta \w'# Rule\0\0'u +\w'NAME\0\0'u +\w'FROM\0\0'u +\w'2006\0\0'u +\w'\*-\0\0'u +\w'Oct\0\0'u +\w'lastSun\0\0'u +\w'2:00\0\0'u +\w'SAVE\0\0'u
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.sp
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# Rule NAME FROM TO \*- IN ON AT SAVE LETTER/S
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-Rule US 2007 max \*- Mar Sun>=8 2:00 1:00 D
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-Rule US 2007 max \*- Nov Sun>=1 2:00 0 S
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-.ta \w'Zone\0\0America/Grand_Turk\0\0'u +\w'STDOFF\0\0'u +\w'RULES\0\0'u +\w'FORMAT\0\0'u
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+Rule US 1967 2006 - Oct lastSun 2:00 0 S
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+Rule US 1967 1973 - Apr lastSun 2:00 1:00 D
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+.ta \w'Zone\0\0America/Menominee\0\0'u +\w'STDOFF\0\0'u +\w'RULES\0\0'u +\w'FORMAT\0\0'u
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# Zone\0\0NAME STDOFF RULES FORMAT [UNTIL]
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-Zone\0\0America/Grand_Turk \*-4:00 \*- AST 2018 Mar 11 2:00
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- \*-5:00 US E%sT
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+Zone\0\0America/Menominee \*-5:00 \*- EST 1973 Apr 29 2:00
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+ \*-6:00 US C%sT
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.sp
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.in
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.fi
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-Here, an incorrect reading would be there were two clock changes on 2018-03-11,
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-the first from 02:00 AST (\*-04) to 01:00 EST (\*-05),
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-and the second an hour later from 02:00 EST (\*-05) to 03:00 EDT (\*-04).
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+Here, an incorrect reading would be there were two clock changes on 1973-04-29,
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+the first from 02:00 EST (\*-05) to 01:00 CST (\*-06),
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+and the second an hour later from 02:00 CST (\*-06) to 03:00 CDT (\*-05).
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However,
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.B zic
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-interprets this more sensibly as a single transition from 02:00 AST (\*-04) to
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-02:00 EDT (\*-04).
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+interprets this more sensibly as a single transition from 02:00 CST (\*-05) to
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+02:00 CDT (\*-05).
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.PP
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A link line has the form
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.sp
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--
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1.8.3.1
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