LDP
/
man-pages
mirror of https://github.com/mkerrisk/man-pages
0
1
Fork 0
Code Releases Activity

tzset.3: Clarify "daylight" and remove erroneous note 

When tzset is run the value of daylight is computed
by looking at all available rules for the application
of daylight savings. This includes reading the tzdata
files to determine if there is a transition or not for
the current timezone. It also includes parsing TZ env
to see if it specifies custom rules which are used in
precedence to any tzdata rules. Therefore daylight is
going to be set if there is a daylight saving rule past,
present, or future that indicates a transition. We clarify
that in the man page.

Lastly, the note about tz_dsttime is not correct and is
removed. The earlier paragraph about daylight makes it
clear that it doesn't mean "daylight saving rule applies
now", and the interaction with tz_dsttime is not correct
for glibc on Linux (as outlined in my gettimeofday.3 patch
sent here: http://marc.info/?l=linux-man&m=144977768703615&w=2).

Signed-off-by: Carlos O'Donell <carlos@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Carlos O'Donell 2015-12-10 17:05:02 -05:00 committed by Michael Kerrisk
parent 53e0c29347
commit 17e9724a2e
1 changed files with 2 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
man3/tzset.3
View File

@ -70,8 +70,8 @@ This function is automatically called by the
other time conversion functions that depend on the timezone.
In a System-V-like environment, it will also set the variables \fItimezone\fP
(seconds West of UTC) and \fIdaylight\fP (to 0 if this timezone does not
have any daylight saving time rules, or to nonzero if there is a time during
the year when daylight saving time applies).
have any daylight saving time rules, or to nonzero if there is a time,
past, present or future when daylight saving time applies).
.PP
If the
.B TZ
@ -223,12 +223,6 @@ T} Thread safety MT-Safe env locale
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
.SH NOTES
Note that the variable \fIdaylight\fP does not indicate that daylight
saving time applies right now.
It used to give the number of some
algorithm (see the variable \fItz_dsttime\fP in
.BR gettimeofday (2)).
It has been obsolete for many years but is required by SUSv2.
.LP
4.3BSD had a function
.BI "char *timezone(" zone ", " dst )