2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
268 lines
5.5 KiB
Groff
268 lines
5.5 KiB
Groff
.\" $NetBSD: tzset.3,v 1.25 2010/12/17 01:29:45 wiz Exp $
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.Dd April 1, 2001
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.Dt TZSET 3
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.Os
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.Sh NAME
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.Nm tzset
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.Nd initialize time conversion information
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In time.h
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.Ft void
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.Fn tzset "void"
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.Sh DESCRIPTION
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The
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.Fn tzset
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function uses the value of the environment variable
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.Ev TZ
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to set time conversion information used by
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.Xr localtime 3 .
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If
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.Ev TZ
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does not appear in the environment,
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the best available approximation to local wall clock time, as
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specified by the
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.Xr tzfile 5
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format file
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.Pa /etc/localtime
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is used by
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.Xr localtime 3 .
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If
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.Ev TZ
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appears in the environment but its value is a null string,
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Coordinated Universal Time (UTC) is used (without leap second
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correction).
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If
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.Ev TZ
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appears in the environment and its value is not a null string:
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.Bl -dash
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.It
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if the value begins with a colon, it is used as a pathname of a file
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from which to read the time conversion information;
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.It
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if the value does not begin with a colon, it is first used as the
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pathname of a file from which to read the time conversion information,
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and, if that file cannot be read, is used directly as a specification
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of the time conversion information.
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.El
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.Pp
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When
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.Ev TZ
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is used as a pathname, if it begins with a slash, it is used as an
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absolute pathname; otherwise, it is used as a pathname relative to
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.Pa /usr/share/zoneinfo .
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The file must be in the format specified in
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.Xr tzfile 5 .
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.Pp
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When
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.Ev TZ
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is used directly as a specification of the time conversion information,
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it must have the following syntax (spaces inserted for clarity):
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.Sm off
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.Bd -literal -offset indent
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.Cm std Cm offset Oo
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.Cm dst Oo
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.Cm offset Oc Oo
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.No , Cm rule Oc Oc
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.Ed
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.Sm on
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.Pp
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where:
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.Bl -tag -width "std and dst" -compact
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.It Cm std No and Cm dst
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Three or more bytes that are the designation for the standard
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.Cm ( std )
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or summer
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.Cm ( dst )
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time zone.
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Only
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.Cm std
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is required; if
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.Cm dst
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is missing, then summer time does not apply in this locale.
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Upper- and lowercase letters are explicitly allowed.
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Any characters except a leading colon (:), digits, comma (,), minus (-),
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plus (+), and ASCII NUL are allowed.
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.It Cm offset
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Indicates the value one must add to the local time to arrive at
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Coordinated Universal Time.
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The
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.Cm offset
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has the form:
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.Sm off
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.Bd -literal -offset indent
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.Cm hh Oo
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.Cm :mm Oo
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.Cm :ss Oc Oc
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.Ed
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.Sm on
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.Pp
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The minutes
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.Cm ( mm )
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and seconds
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.Cm ( ss )
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are optional.
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The hour
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.Cm ( hh )
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is required and may be a single digit.
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The
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.Cm offset
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following
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.Cm std
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is required.
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If no
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.Cm offset
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follows
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.Cm dst ,
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summer time is assumed to be one hour ahead of standard time.
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One or more digits may be used; the value is always interpreted as a
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decimal number.
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The hour must be between zero and 24, and the minutes (and
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seconds) \(em if present \(em between zero and 59.
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If preceded by a
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.Dq -
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the time zone shall be east of the Prime Meridian; otherwise it shall be
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west (which may be indicated by an optional preceding
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.Dq + ) .
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.It Cm rule
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Indicates when to change to and back from summer time.
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The
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.Cm rule
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has the form:
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.Sm off
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.Bd -literal -offset indent
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.Xo
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.Cm date No /
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.Cm time No ,
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.Cm date No /
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.Cm time
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.Xc
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.Ed
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.Sm on
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.Pp
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where the first
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.Cm date
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describes when the change from standard to summer time occurs and the
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second
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.Cm date
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describes when the change back happens.
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Each
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.Cm time
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field describes when, in current local time, the change to the other
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time is made.
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The format of
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.Fa date
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is one of the following:
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.Bl -tag -width "The Julian day" -compact
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.It Cm J Ns Ar n
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The Julian day
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.Ar n
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(1 \*[Le]
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.Ar n
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\*[Le] 365).
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Leap days are not counted; that is, in all years \(em including leap
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years \(em February 28 is day 59 and March 1 is day 60.
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It is impossible to explicitly refer to the occasional February 29.
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.It Ar n
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The zero-based Julian day (0\ \*[Le]
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.Ar n
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\*[Le]\ 365).
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Leap days are counted, and it is possible to refer to
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February 29.
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.Sm off
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.It Cm M Ns Ar m No . Ar n No . Ar d
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.Sm on
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The
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.Ar d Ns 'th
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day
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(0 \*[Le]
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.Ar d
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\*[Le]\ 6) of week
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.Ar n
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of month
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.Ar m
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of the year
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(1 \*[Le]
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.Ar n
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\*[Le]\ 5, 1 \*[Le]
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.Ar m
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\*[Le]\ 12, where week 5 means
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.Dq the\ last Ar d No day\ in\ month Ar m
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which may occur in either the fourth or the fifth week).
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Week 1 is the first week in which the
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.Ar d Ns 'th
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day occurs.
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Day zero is Sunday.
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.El
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The
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.Cm time
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has the same format as
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.Cm offset
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except that no leading sign
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.Dq -
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or
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.Dq +
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is allowed.
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The default, if
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.Cm time
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is not given, is
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.Cm 02:00:00 .
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.El
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If no
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.Cm rule
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is present in
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.Ev TZ ,
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the rules specified by the
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.Xr tzfile 5
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format file
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.Pa posixrules
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in
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.Pa /usr/share/zoneinfo
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are used, with the standard and summer time offsets from UTC replaced
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by those specified by the
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.Cm offset
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values in
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.Ev TZ .
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.Pp
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For compatibility with System V Release 3.1, a semicolon (;) may be
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used to separate the
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.Cm rule
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from the rest of the specification.
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.Pp
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If the
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.Ev TZ
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environment variable does not specify a
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.Xr tzfile 5
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format file and cannot be interpreted as a direct specification, UTC
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is used.
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.Sh FILES
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.Bl -tag -width /usr/share/zoneinfo/posixrules -compact
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.It Pa /etc/localtime
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local time zone file
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.It Pa /usr/share/zoneinfo
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time zone information directory
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.It Pa /usr/share/zoneinfo/posixrules
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used with POSIX-style TZ's
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.It Pa /usr/share/zoneinfo/GMT
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for UTC leap seconds
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.El
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.Pp
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If
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.Pa /usr/share/zoneinfo/GMT
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is absent, UTC leap seconds are loaded from
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.Pa /usr/share/zoneinfo/posixrules .
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.Sh SEE ALSO
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.Xr ctime 3 ,
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.Xr getenv 3 ,
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.Xr strftime 3 ,
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.Xr time 3 ,
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.Xr tzfile 5
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.Sh STANDARDS
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The
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.Fn tzset
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function conforms to
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.St -p1003.1-88 .
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.\" @(#)newtzset.3 8.2
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.\" This file is in the public domain, so clarified as of
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.\" 2009-05-17 by Arthur David Olson.
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