tzset \- initialize time conversion information
uses the value of the environment variable
to set time conversion information used by
does not appear in the environment,
the best available approximation to local wall clock time, as specified
in the system time conversion information directory, is used by
appears in the environment but its value is a null string,
Coordinated Universal Time (UTC) is used (without leap second
appears in the environment and its value is not a null string:
if the value begins with a colon, it is used as a pathname of a file
from which to read the time conversion information;
if the value does not begin with a colon, it is first used as the
pathname of a file from which to read the time conversion information,
and, if that file cannot be read, is used directly as a specification of
the time conversion information.
is used as a pathname, if it begins with a slash,
it is used as an absolute pathname; otherwise,
it is used as a pathname relative to a system time conversion information
The file must be in the format specified in
is used directly as a specification of the time conversion information,
it must have the following syntax (spaces inserted for clarity):
\fIstd\|offset\fR[\fIdst\fR[\fIoffset\fR][\fB,\fIrule\fR]]
Three or more bytes that are the designation for the standard
is missing, then summer time does not apply in this locale.
Upper- and lowercase letters are explicitly allowed. Any characters
and ASCII NUL are allowed.
Indicates the value one must add to the local time to arrive at
Coordinated Universal Time. The
\fIhh\fR[\fB:\fImm\fR[\fB:\fIss\fR]]
is required and may be a single digit. The
summer time is assumed to be one hour ahead of standard time. One or
more digits may be used; the value is always interpreted as a decimal
number. The hour must be between zero and 24, and the minutes (and
seconds) \(em if present \(em between zero and 59. If preceded by a
the time zone shall be east of the Prime Meridian; otherwise it shall be
west (which may be indicated by an optional preceding
Indicates when to change to and back from summer time. The
\fIdate\fB/\fItime\fB,\fIdate\fB/\fItime\fR
describes when the change from standard to summer time occurs and the
describes when the change back happens. Each
field describes when, in current local time, the change to the other
.RI "(1\ \(<=" "\ n\ " "\(<=\ 365).
Leap days are not counted; that is, in all years \(em including leap
years \(em February 28 is day 59 and March 1 is day 60. It is
impossible to explicitly refer to the occasional February 29.
The zero-based Julian day
.RI "(0\ \(<=" "\ n\ " "\(<=\ 365).
Leap days are counted, and it is possible to refer to February 29.
.RI "(0\ \(<=" "\ d\ " "\(<=\ 6)
.RI "(1\ \(<=" "\ n\ " "\(<=\ 5,
.RI "1\ \(<=" "\ m\ " "\(<=\ 12,
where week 5 means ``the last
which may occur in either the fourth or the fifth week). Week 1 is the
day occurs. Day zero is Sunday.
except that no leading sign
is allowed. The default, if
in the system time conversion information directory are used, with the
standard and summer time offsets from UTC replaced by those specified by
For compatibility with System V Release 3.1, a semicolon
may be used to separate the
from the rest of the specification.
environment variable does not specify a
and cannot be interpreted as a direct specification,
.ta \w'/usr/local/etc/zoneinfo/posixrules\0\0'u
/usr/local/etc/zoneinfo time zone information directory
/usr/local/etc/zoneinfo/localtime local time zone file
/usr/local/etc/zoneinfo/posixrules used with POSIX-style TZ's
/usr/local/etc/zoneinfo/GMT for UTC leap seconds
.B /usr/local/etc/zoneinfo/GMT
UTC leap seconds are loaded from
.BR /usr/local/etc/zoneinfo/posixrules .