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2007 Daylight Savings Time Problem
Contents 1. Intro and General Information 2. Windows 3. Macs
4. Unix 5. PDAs 6. Applications 7. UICalendar

2007 Daylight Savings Time Changes for Unix


In 2005, the United States congress passed the Energy Policy Act of 2005, which among other things extended the duration of Daylight Savings Time in United States, starting in 2007. Canada and Bermuda have followed suit.

The problem is that, during the extended periods of three weeks in the spring and one week in the fall, many clocks on systems which automatically to change to and from Daylight Savings Time will continue to operate on Standard Time, even though Daylight Time is actually in effect. These uncorrected systems will not be synchronized with other systems which have been fixed.

This page tells you how to correct that, so that the automatic Daylight Time changes take place on the correct date.

We have until March 11, 2007 to fix this problem in the U.S. and Canada.

  Linux uses Zoneinfo data. Here are updates:  
  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.
  1. Apply correcting APARs from IBM for the latest supported versions
  2. 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 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 This APAR is also included in level 5300-05-05.
  • APAR IY91985 for AIX 5.2. This will provide fileset
  • 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

Sun Solaris
  Sun Microsystems: "Daylight Saving Time (DST) Changes for Australia (2006), United States (2007) and Others"

There are four issues highlighted in that article:

  1. Unix Timezone data needs to be updated. If solaris patches cannot be installed, you can also temporarily set the TZ environment variable: TZ=CST6CDT,M3.2.0,M11.1.0
  2. Some Sun mid-range servers require firmware patches to correct the system controller.
    Sun Alert ID: 102617 - Required Server Firmware for Timezone Changes Due to U.S. Energy Policy Act of 2005
  3. Patches to the Rogue Wave Tools.h++ library that is included with Sun C++ are at Sun Alert 102754
  4. Java issues, described at Overview and Mitigation of the USA2007DST Issue for the Java SE platform and Solaris OS
See Also

The notes under 3. General Considerations on the introduction page. Various information there applies to Unix.


DST Problem Previous:  3. Macs Next:  5. PDAs

2007-2-24  ACCC documentation
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