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Document TZ transition times >= 25:00:00.

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* manual/time.texi (TZ Variable): Document transition times from
25:00:00 through 167:59:59.  These are already supported, and this
support will help with version-3 tz-format files.
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Paul Eggert 2013-09-18 13:01:11 -07:00
parent 69947401b9
commit 4480e934cc
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5
ChangeLog
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@ -1,5 +1,10 @@
2013-12-17 Paul Eggert <eggert@cs.ucla.edu>
Document TZ transition times >= 25:00:00.
* manual/time.texi (TZ Variable): Document transition times from
25:00:00 through 167:59:59. These are already supported, and this
support will help with version-3 tz-format files.
* manual/time.texi (TZ Variable): Modernize North America example
to reflect current (i.e., 2007-and-later) daylight saving rules.

27
manual/time.texi
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@ -2086,9 +2086,11 @@ between @code{1} and @code{12}.
The @var{time} fields specify when, in the local time currently in
effect, the change to the other time occurs. If omitted, the default is
@code{02:00:00}.
@code{02:00:00}. The hours part of the time fields can range from
0 through 167; this is an extension to POSIX.1, which allows
only the range 0 through 24.
Here is an example @code{TZ} value, including the appropriate
Here are some example @code{TZ} values, including the appropriate
Daylight Saving Time and its dates of applicability. In North
American Eastern Standard Time (EST) and Eastern Daylight Time (EDT),
the normal offset from UTC is 5 hours; since this is
@ -2100,6 +2102,27 @@ at 2:00am.
EST+5EDT,M3.2.0/2,M11.1.0/2
@end smallexample
Israel Standard Time (IST) and Israel Daylight Time (IDT) are 2 hours
ahead of the prime meridian in winter, springing forward an hour on
March's fourth Tuesday at 26:00 (i.e., 02:00 on the first Friday on or
after March 23), and falling back on October's last Sunday at 02:00.
@smallexample
IST-2IDT,M3.4.4/26,M10.5.0
@end smallexample
Western Argentina Summer Time (WARST) is 3 hours behind the prime
meridian all year. There is a dummy fall-back transition on December
31 at 25:00 daylight saving time (i.e., 24:00 standard time,
equivalent to January 1 at 00:00 standard time), and a simultaneous
spring-forward transition on January 1 at 00:00 standard time, so
daylight saving time is in effect all year and the initial @code{WART}
is a placeholder.
@smallexample
WART4WARST,J1/0,J365/25
@end smallexample
The schedule of Daylight Saving Time in any particular jurisdiction has
changed over the years. To be strictly correct, the conversion of dates
and times in the past should be based on the schedule that was in effect