Updating System i5 for Daylight Saving time changes:

In the Energy Policy Act of 2005, Congress changed Daylight Saving Time (DST) in the United States so that starting this year (2007) DST begins three weeks earlier than it did last year, on the second Sunday of March. Conversely, 2007 will also see Daylight Saving Time end one week later than last year, on the first Sunday in November.

There are two ways to handle this change. You can do a manual adjustment or you can apply IBM's new Daylight Saving Time PTFs for i5 systems running i5/OS V5R3 and V5R4.
• For i5/OS V5R4, order PTFs SI26040 and SI25990
• For i5/OS V5R3, order PTFs SI26039 and SI25991
The PTFs automate the changes needed to support the new DST rules. After application, all of the time zone rules on the system will be updated to the new DST starting and ending dates.

After applying the PTF upgrade, you can check to see if the fix has been applied by performing the following steps on all your upgraded partitions:

1. Double-check the Time Zone description that your partition is using by referencing the QTIMZON system value. On a 5250 green screen, you can check this value by using this Display System Value command (DSPSYSVAL).

DSPSYSVAL SYSVAL(QTIMZON)

2. Look up the Daylight Saving Time start and end date for your time zone value by using the Work with Time Zone Descriptions command (WRKTIMZON). Run this command to display all Time Zone descriptions on your system, like this:

WRKTIMZON TIMZON(*ALL)

The Work with Time Zone Descriptions screen will display all the different time zones that are defined on your system.
To find your QTIMZON time zone on the WRKTIMZON screen, page down the list until you see either the time zone listed in QTIMZON or a time zone with a greater than sign (>) in front of it (the default time zone will always be designated in this list by a '>' sign). Place a 5=Display details in front of your default time zone entry and press Enter. On the screens that follow, you will see the starting and ending DST dates for your time zone description. What you are interested in is whether or not the PTFs changed your time zone DST start and end dates correctly.

If your time zone rule could not be changed by the PTF upgrade (as explained above), then you should change it manually by entering the following Change Time Zone Description command (CHGTIMZON) and pressing the F4 key.

CHGTIMZON TIMZON(TIME_ZONE_DESCRIPTION_NAME)

Locate the DST start and end dates on the second CHGTIMZON screen (which can be accessed by pressing the F24=More key on the first screen, followed by the F9=All key). If your time zone DST dates were not changed, you can change them manually from this screen.