AIX Tip of the Week

Subject: US Daylight Savings Time Change Beginning in 2007

Audience: All

Update: October 27, 2006

Just a reminder. In 2007 the Daylight Saving Time start/end dates will change in the United States. The new start date is the second Sunday of March; the new end date is the first Sunday of November. For more information, see "Managing the Time Zone Variable" at

You'll need one of the the following APARs:

Some of the more current AIX releases already have this patch. You can use the instfix command to determine whether your system already has this fix installed. For example, if you have AIX 5.3, the command would be: instfix -iak IY75211

If not, you can down load it from Fix Central:

Comment: Plan ahead, this isn't a simple patch. Fix Central added 800 MB of prereq's when I went to download IY75211 for my AIX 5.3 ML3 system.

Date: January 31, 2006

On August 8, 2005, President George W. Bush signed the Energy Policy Act of 2005. This Act changed the time change dates in the U.S. Beginning in 2007

AIX development will be releasing APARs to change the current AIX behavior. A workaround will also be published for AIX 4.3 since it is out of service.

The United States official Daylight Saving Time begin and end dates have changed as of the year 2007. The new start date is the second Sunday of March; the new end date is the first Sunday of November.

The APARs are:

Also, at this time, I do not have any information on AIX 4.3 workaround.

Update 4/2/06

The following URL discusses a possible workaround for AIX 4.3

Note: fileset controls the timezone variable.

Update November 20, 2006

AIX Time Zone updates will require that every AIX server must be updated in some way prior to March 11, 2007.

AIX fix levels may need to be upgraded before the specific fix can be installed. For instance the 5.3 APAR requires TL4. The 5.2 APAR requires TL8. Any attempt to package the fix at an earlier ML will result in the message:

The fixes selected cannot be received without upgrading to a newer Technology Level. To download the fixes, uncheck the box labeled:
"Keep me at my current Technology Level (oslevel)."

If the system can not be updated to the required level by March 11, 2007; the best option is to set the TZ environment variable in /etc/environment.

Full instructions are available at:

Additional Info:

Update: November 26, 2006

The United States official Daylight Saving Time (DST) begin and end dates are changing as of next year. The new start date is the second Sunday of March; the new end date is the first Sunday of November. In 2007, DST starts on March 11 and ends on November 4.

AIX requires fixes to implement the official DST change in 2007. Those fixes should be installed prior to March 11, 2007.

See the Managing the Time Zone Variable web page (at ) for a list of recommended APAR fixes. As noted on the web page, a fix to change DST begin and end dates is included in Technology Level 5200-08 (and later) and Technology Level 5300-04 (and later). (Susan Walz has remarked that, given the number of prereqs for the APAR fixes, in most cases it is simpler to move to the appropriate TL rather than attempt to apply fixes for individual APARs.) The cited web page also describes how to implement the DST change without a fix by setting the TZ environment variable appropriately. If /etc/environment is edited to change the TZ setting, then all running processes affected by the change must be stopped and restarted. The simplest way to guarantee that all affected processes are stopped and restarted is to reboot AIX.

Please note that HMC machine code below the V6.1 level also requires a patch. The Hardware Management Console support web page (at ) has a Daylight Savings Time rule changes and HMC updates link. The Time Zone notice web page reached by the link lists the fix packages required. (The web page states that certain Indiana counties moved from Eastern time to Central time coincident with the change to DST back in 2006, which unfortunately dilutes the message that patches must be applied to all HMCs which are configured to display time in a U.S. time zone to which DST applies, not merely those HMCs which are configured to display time in certain Indiana counties.)

Please note that DST fixes and patches do not alter the system clock. They alter the way in which the system clock is displayed and interpreted. So if DST is not implemented correctly, cron jobs will still run, but may run an hour earlier or later than expected if they are scheduled to run based on local time.

Middleware patches are sometimes also required to implement the DST change.

For example, Java SDKs and RTEs require a patch. See the Changes to Daylight Saving Time (DST) affect IBM SDKs for Java web page (at ) for more information.

But please note that if Java is delivered and installed as part of an IBM middleware product, refer to product support information for that product to learn about upgrading. So, for example, if Java is delivered and installed via WebSphere, see the Daylight Saving Time (DST) 2007 information for WebSphere Application Server web page (at ) for more information.

DB2 is another example of middleware which needs to be patched.

See the Software products impacted by Daylight Saving Time in 2007 web page (at ) for a list of all affected products and links to sources of additional information.

Update: December 17, 2006

The following table describes the PTF required to apply on your HMC, in order for the time to change correctly on the HMC, according to the new DST rules. Reference the HMC Support web site for more info on the HMC Version and associated PTFs at:

HMC Version	Package(s) that must be installed
HMC 6.1	There is no need to install additional package
HMC 5.2	APAR MB01365 / PTF MH00586
HMC 5.1	APAR MB001275 / PTF MH00493
HMC 4.5	APAR MB001276 / PTF MH00494
HMC 3.3.7	APAR IY87070 / PTF U808917
HMC 3.3.6	APAR IY79212 / PTF U806370


Update: January 10, 2007

DST website for all IBM products.

Bruce Spencer,

January 31, 2006