For the first time in two decades, the United States has changed Daylight Savings Time (DST). The change, intended to decrease energy consumption, comes from a provision of the Energy Policy Act of 2005 that extends DST by four weeks beginning in 2007. This year, DST starts three weeks earlier on the second Sunday in March (March 11), and ends one week later on the first Sunday in November (November 4). Canada and Bermuda have also adopted the change.

The time change affects V5R4 and V5R3 of i5/OS, as well as any other computer system or application that is dependent on the accuracy of time-senstive information or transactions. Organizations in countries that work with systems in the U.S., Canada, or Bermuda may also need to take a look at their systems and applications.

The updates for DST for i5/OS are available as:

• V5R4M0 SI26040 and SI25990
• V5R3M0 SI26039 and SI25991

Once the PTF is loaded and installed on a system, the new DST rules will be in effect, IBM says, noting that these PTFs are immediate and will not require a system IPL.

If you are running an earlier version of i5/OS, you don't need an i5/OS-related update because IBM added automatic DST support starting with V5R3. In addition, if you're using Java, International Components for Unicode (ICU), or the Hardware Management Console (HMC), IBM has additional DST fixes for you.

Of course, if your applications utilize DST rules, you'll need to consider how they function with your system clock and the new dates. If you miss something, your applications will only be off by one hour for four weeks . . . which might be a neglible problem for some while critical for others.

To learn more, go to http://www.ibm.com/support/alerts/operatingsystem/us.