[tz] [PATCH] Improve doc of zic coalescing zone+DST transitions
eggert at cs.ucla.edu
Tue Dec 22 23:12:16 UTC 2020
* zic.8: Improve documentation for how certain transitions
are coalesced. Also, use current data for America/Menominee
instead an America/Grand_Turk entry that not in current data.
Improvements suggested by Tim Parenti.
zic.8 | 36 +++++++++++++++++++++---------------
1 file changed, 21 insertions(+), 15 deletions(-)
diff --git a/zic.8 b/zic.8
index 2273dad..60262d7 100644
@@ -590,35 +590,41 @@ first transition into standard time.
In a single zone it is an error if two rules take effect at the same
instant, or if two zone changes take effect at the same instant.
-If a continuation line subtracts from the UT offset after a transition that
-would be interpreted to be later if using the continuation line's rules, the
+If a continuation line subtracts
+seconds from the UT offset after a transition that would be
+interpreted to be later if using the continuation line's UT offset and
-time of the earlier zone or continuation line is interpreted according
-to the continuation line's rules.
+time of the previous zone or continuation line is interpreted
+according to the continuation line's UT offset and rules, and any rule
+that would otherwise take effect in the next
+seconds is instead assumed to take effect simultaneously.
-.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
+.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
# Rule NAME FROM TO \*- IN ON AT SAVE LETTER/S
-Rule US 2007 max \*- Mar Sun>=8 2:00 1:00 D
-Rule US 2007 max \*- Nov Sun>=1 2:00 0 S
-.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
+Rule US 1967 2006 - Oct lastSun 2:00 0 S
+Rule US 1967 1973 - Apr lastSun 2:00 1:00 D
+.ta \w'Zone\0\0America/Menominee\0\0'u +\w'STDOFF\0\0'u +\w'RULES\0\0'u +\w'FORMAT\0\0'u
# Zone\0\0NAME STDOFF RULES FORMAT [UNTIL]
-Zone\0\0America/Grand_Turk \*-4:00 \*- AST 2018 Mar 11 2:00
- \*-5:00 US E%sT
+Zone\0\0America/Menominee \*-5:00 \*- EST 1973 Apr 29 2:00
+ \*-6:00 US C%sT
-Here, an incorrect reading would be there were two clock changes on 2018-03-11,
-the first from 02:00 AST (\*-04) to 01:00 EST (\*-05),
-and the second an hour later from 02:00 EST (\*-05) to 03:00 EDT (\*-04).
+Here, an incorrect reading would be there were two clock changes on 1973-04-29,
+the first from 02:00 EST (\*-05) to 01:00 CST (\*-06),
+and the second an hour later from 02:00 CST (\*-06) to 03:00 CDT (\*-05).
-interprets this more sensibly as a single transition from 02:00 AST (\*-04) to
-02:00 EDT (\*-04).
+interprets this more sensibly as a single transition from 02:00 CST (\*-05) to
+02:00 CDT (\*-05).
A link line has the form
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