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Operating Systems AIX Timezone issues -- Daylight savings Post 302988067 by filosophizer on Tuesday 20th of December 2016 07:47:30 AM
Old 12-20-2016
There is a difference in timezone setting in AIX 5.3 vs AIX 6.1

For AIX 5.3, if you are using timezone with daylight savings then you would need to enable it, and also you need to apply the apar for it
Quote:
DST for UNIX
IBM AIX
There are two methods to make the AIX Unix operating system change to Daylight Savings Time on the new dates. The patches change the default dates, and the TZ variable, if set, overrides whatever the default dates are. You may use either method by itself. and doing both will not cause a conflict.
Apply correcting APARs from IBM for the latest supported versions
Modify the TZ variable in the /etc/environment file.
Either method requires a system reboot prior to March 11, 2007 to take effect.
Note that all of the patches mentioned in this section can be applied at once to AIX by updating to level 5300-05-05.

The TZ variable method might be preferable where you do not want to change or update anything else; you just want to fix the Daylight Time change dates. Setting the TZ environment variable should be regarded as a temporary measure until more permanent patches can be installed. Both methods are described on these IBM web pages:

AIX O/S updated to support 2007 Daylight Saving Time change
IBM AIX: Managing the Time Zone Variable
AIX also contains time zone information in directory /usr/share/lib/zoneinfo which is used only by the zdump command. This information is not used by any other parts of the system itself, though it is used by the MySQL database system, and possibly other application programs. The following IBM APARs address these Unix Zoneinfo data files to insure that the zdump command will return correct output:

APAR IY91662 for AIX 5.3. This will provide fileset bos.rte.date.5.3.0.51. This APAR is also included in level 5300-05-05.
APAR IY91985 for AIX 5.2. This will provide fileset bos.rte.date.5.2.0.41.
The zdump command and the /usr/share/lib/zoneinfo data did not exist in AIX prior to 5.2.
Be sure not to ignore the additional issues in IBM Java, described here:
Changes to Daylight Saving Time will affect IBM Java and AIX
AIX 6.1 takes the daylight timings automatically, when the date comes for time backward/forward, it does it automatically, see zdump
so there is no setting to turn on or turn off the DST in AIX 6.1 and higher.

Question:
CST6CDT (POSIX) and America/Chicago (Olson)

I have read both are same timezones, so what difference does it make ?

Quote:
Each of the following examples shows the three different ways that the four American time zones can be specified:
America/New York or EST or EST5EDT
America/Chicago or CST or CST6CDT
America/Denver or MST or MST7MDT
America/Los_Angeles or PST or PST8PDT

For parts of the Unites States that do not observe daylight savings time or have different daylight savings time rules, specify the appropriate "America/City" selection, for example:
America/Indianapolis for those parts of the state of Indiana that are in the Eastern Time Zone.
America/Phoenix is used for the entire state of Arizona, which does not observe any daylight savings time.
 

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zdump(1M)						  System Administration Commands						 zdump(1M)

NAME
zdump - time zone dumper SYNOPSIS
zdump [--version] [-v] [-c [loyear,]hiyear] [zonename]... DESCRIPTION
The zdump command prints the current time for each time zone (zonename) listed on the command line. Specify zonename as the name of the time zone database file relative to /usr/share/lib/zoneinfo. Specifying an invalid time zone (zonename) to zdump does not return an error, rather zdump uses GMTO. This is consistent with the behavior of the library calls; zdump reflects the same behavior of the time routines in libc. See ctime(3C) and mktime(3C). OPTIONS
The following options are supported: --version Outputs version information and exits. -v Displays the entire contents of the time zone database file for zonename. Prints the time at the lowest possible time value; the time one day after the lowest possible time value; the times both one second before and exactly at each time at which the rules for computing local time change; the time at the highest possible time value; and the time at one day less than the highest possible time value. See mktime(3C) and ctime(3C) for information regarding time value (time_t). Each line of output ends with isdst=1 if the given time is Daylight Saving Time, or isdst=0 otherwise. -c [loyear],hiyear Cuts off the verbose output near the start of the given year(s) . By default, the program cuts off verbose output near the start of the years -500 and 2500. EXIT STATUS
The following exit values are returned: 0 Successful completion. 1 An error occurred. FILES
/usr/share/lib/zoneinfo Standard zone information directory ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ |Interface Stability |Stable | +-----------------------------+-----------------------------+ SEE ALSO
zic(1M), ctime(3C), mktime(3C), attributes(5), environ(5) SunOS 5.11 3 Jan 2006 zdump(1M)
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