Setting the TZ at aix.4.1.5

Setting the TZ at aix.4.1.5

Post by Moty Moya » Thu, 12 Oct 2000 04:00:00

Hello everybody,

I'm looking for information how to set up the TZ variable for the daylight
saving time.
The information that I'm looking for is how to use the Julian calander at
the TZ for the
date of the daylight saving.



Setting the TZ at aix.4.1.5

Post by Jan Muenc » Thu, 12 Oct 2000 04:00:00

Moty Moyal wrote:
> Hello everybody,

> I'm looking for information how to set up the TZ variable for the daylight
> saving time.
> The information that I'm looking for is how to use the Julian calander at
> the TZ for the
> date of the daylight saving.

> Thnks

Hi Moty,

I have found a detailed description in Docsearch:

environment File


Sets up the user environment.


The /etc/environment file contains variables specifying the basic environment
for all processes. When a new process begins, the exec subroutine makes an
array of strings available that have the form Name=Value. This array of
strings is called the environment. Each name defined by one of the strings is
called an environment variable or shell variable. The exec subroutine allows
the entire environment to be set at one time.

Environment variables are examined when a command starts running. The
environment of a process is not changed by altering the /etc/environment
file. Any processes that were started prior to the change to the
file must be restarted if the change is to take effect for those processes.
If the TZ variable is changed, the cron daemon must be restarted, because
this variable is used to determine the current local time.

The following restrictions apply, when modifying the environment file:

      Ensure that newly created environment variables do not conflict with
standard variables such as MAIL, PS1, PS2, and IFS.
      Ensure that the information in the environment file is in the
Name=Value format. Unlike profile scripts, the environment file is not a
shell script and does not accept data in any format other than the Name=Value


               The time-zone information. The TZ environment variable is set
by the /etc/environment file. The TZ environment variable has the following
format (spaces inserted for readability):

               std offset dst offset , rule

               The fields within the TZ environment variable are defined as

               std and dst
                        Designate the standard (std) and summer (dst) time
zones. Only the std value along with the appropriate offset value is
required. If the dst value is not specified, summer time does not apply. The
                        values specified may be no less than three and no
more than TZNAME_MAX bytes in length. The length of the variables corresponds
to the %Z field of the date command; for libc and libbsd,
                        TZNAME_MAX equals three characters. Any nonnumeric
ASCII characters except the following may be entered into each field: a
leading : (colon), a , (comma), a - (minus sign), a + (plus sign),
                        or the ASCII null character.

                              Note: POSIX 1.0 reserves the leading : (colon)
for an implementation-defined TZ specification. AIX disallows the leading
colon, selecting CUT0 and setting the %Z field to a null

                        An example of std and dst format is as follows:


               Specifies Eastern U.S. standard time.
               Specifies the offset, which is 5 hours behind Coordinated
Universal Time (CUT).
                   Specifies the corresponding summer time zone abbreviation.

                    Note: See "Time Zones" for a list of time zone names
defined for the system.

                     Denotes the value added to local time to equal
Coordinated Universal Time (CUT). CUT is the international time standard that
has largely replaced Greenwich Mean Time. The offset variable has the
                     following format:


                     The fields within the offset variable are defined as

               Specifies the dst offset in hours. This field is required. The
hh value can range between the integers -12 and +11. A negative value
indicates the time zone is east of the prime meridian; a positive value or no

               value indicates the time zone is west of the prime meridian.
               Specifies the dst offset detailed to the minute. This field is
optional. If the mm value is present, it must be specified between 0 and 59
and preceded by a : (colon).
                  Specifies the dst offset detailed to the second. The ss
field is optional. If the ss value is present, it must be specified between 0
and 59 and preceded by a : (colon).

               An offset variable must be specified with the std variable. An
offset variable for the dst variable is optional. If no offset is specified
with the dst variable, the system assumes that summer time is one hour
               ahead of standard time.

               As an example of offset syntax, Zurich is one hour ahead of
CUT, so its offset is -1. Newfoundland is 1.5 hours ahead of eastern U.S.
standard time zones. Its syntax can be stated as any of the following: 3:30,
               03:30, +3:30, or 3:30:00.

                   The rule variable indicates when to change to and back
from summer time. The rule variable has the following format:


                   The fields within the rule variable are defined as

               Specifies the change from standard to summer time.
               Specifies the return to standard time from summer time.
               Specifies when the time changes occur within the time zone.
For example, if the time variable is encoded for 2 a.m. then the time changes
when the time zone reaches 2 a.m. on the date specified in the start
               Delimits the start date, end date, and time variables.
                  (Comma) Delimits two date and time pairs.

               The start and end variables support a syntax for Julian time
(J) and a syntax for leap years (M):


               In the J syntax, the n variable has the value of 1 through
365. Leap days are not counted. In the M syntax, m is the month, n the week,
and d the day of the week starting from day 0 (Sunday).

               The rule variable has the same format as the offset variable
except no leading - (minus sign) or + (plus sign) is allowed. The default of
the start variable is 02:00:00 (2 a.m.).

                    Note: The time zone offsets and time change points are
interrelated and context-dependent. The rule variable's runtime execution
semantics change as a function of the offsets. For example, if
                    the summer time zone changes one hour, as in CST6CDT5,
(the default 2 a.m.) summer time changes instantaneously from 2 a.m. to 3
a.m. CDT. The fall change is from 2 a.m. CDT to 1 a.m. CST.
                    The respective changes for a time zone of CST6CDT4 are 2
a.m. CST to 4 a.m. CDT and 2 a.m. CDT to 12 a.m. CST.

               In an example of the rule variable, if the law changed so that
the Central United States experienced summer time between Julian 129 and
Julian 131, the TZ variable would be stated as follows:


               In this example, the dates indicated are May 09 and May
11,1993, respectively. (Use the date +%j command to get the Julian date

               In another example, if the time changes were to occur at 2
a.m. CST and 19:30 CDT, respectively, the variables would be stated as


               In nonleap years, the fallback time change would be from 19:30
CDT to 18:30 CST on May 11 (1993).

               For the leap year (M) syntax, the spring ahead date would be 2
May and the fallback date is 9 May. The variables are stated as follows:


Time Zones

The system defines the following time zones and time zone names:

      Note: Coordinated Universal Time (CUT) is the international time

 Time Zones Defined on the System
                      Time Zone
                                              CUT Offset
                      Coordinated Universal Time
                      United Kingdom
                      Azores, Cape Verde
                                              CUT -1
                      Falkland Islands
                                              CUT -2
                      Greenland, East Brazil
                                              CUT -3
                      Central Brazil
                                              CUT -4
                      Eastern United States, Colombia
                                              CUT -5
                      Central United States, Honduras
                                              CUT -6
                      Mountain United States
                                              CUT -7
                      Pacific United States, Yukon
                                              CUT -8
                                              CUT -9
                      Hawaii, Aleutian Islands
                                              CUT -10
                      Bering Strait
                                              CUT -11
                      New Zealand
                                              CUT +12
                      Solomon Islands
                                              CUT +11
                      Eastern Australia
                                              CUT +10

read more »


Setting the TZ at aix.4.1.5

Post by Villy Kru » Thu, 12 Oct 2000 04:00:00

Unfortunately, all these doesn't use the right rules for changing to
summer time, except for the US timezones.  

Thus for UK time zone you need


M3.5.0/1  Means change at month 3 week 5 day 0 at 01:00 local time
M10.5.0/2 Means change at month 10 week 5 day 0 at 02:00 local summer time.
Week 5 is defined as last week in any month regardless on how many weeks
it actualy has, and day 0 is Sunday morning.

BTW, the common acronyme for Coordinated Universal Time is UTC.


> Time Zones Defined on the System
> Name
>                      Time Zone
>                                              CUT Offset
>                      Coordinated Universal Time
>                                              CUT
>                      United Kingdom
>                                              CUT
>                      Azores, Cape Verde
>                                              CUT -1
>                      Falkland Islands
>                                              CUT -2
>                      Greenland, East Brazil
>                                              CUT -3


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