* 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 --- a/zic.8 +++ b/zic.8 @@ -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. .PP -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 +.I N +seconds from the UT offset after a transition that would be +interpreted to be later if using the continuation line's UT offset and +rules, the .q "until" -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 +.I N +seconds is instead assumed to take effect simultaneously. For example: .br .ne 7 .nf .in +2m -.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 .sp # 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 .sp .in .fi -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). However, .B zic -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). .PP A link line has the form .sp -- 2.27.0