HP 3000's extended time gets posted
Where is Integrity on its takeover curve?

Making a time shift on the 3000

Last weekend, HP 3000 customers saw the last of the switch-to-standard time during a month of October. Citing a desire to conserve energy by keeping the lights off as long as possible, US government officials have changed the switchover times for both "fall back" and "spring forward." HP has sprung into action to accomodate the changes on the HP 3000.

As always, customers can fall back on the community's keen eye for detail to ensure HP's time zone engineering gets onto the systems in plenty of time. After HP's Bill Cadier announced HP has created the file needed to embrace the new mid-March and early-November dates for Daylight Saving, 3000 community members pointed to related information both supplemental and incidental.

Donna Hofmeister of the OpenMPE board of directors says another director — apparently wanting to remain anonymous — thinks somebody in HP doesn't understand how the magic TZTAB.LIB file does its work.

Donna reported that the OpenMPE director said, "The author of the HP Web page seems not to understand the TZTAB function.  In the section “Maintaining TZTAB” HP states:

Under Section 110 of the Energy Policy Act of 2005, the Secretary of the U.S. Department of Energy must make a report to the Congress on the effectiveness of the daylight saving time changes on energy consumption in the US no later than 9 months after its implementation. The Congress of the United States reserves the right to revert the daylight saving time rules to those implemented in 1986 and in use through 2006 based on that report. Should Congress opt to revert U.S. daylight saving time to the pre-2007 rules, this change will probably take effect after the end of MPE/iX support on 31 December 2008. This is why we recommend retaining a copy of the current (pre-2007) TZTAB.

The director continued, "In the event that Congress decides to undo the DST rules, it won’t undo the time relationships between UCT and Local for timestamps applied during the period in which the new rules were in effect, so we can NEVER return to the current TZTAB; so retaining a copy of the current TZTAB for the purpose of someday restoring it is nonsensical. If the DST rules are in fact reverted to the old rules, then the TZTAB will simply grow longer, not shorter.

"Once you have tested the new TZTAB installation, you could keep the current TZTAB for historical or sentimental reasons, but make sure it is in a safe place where it will not be confused with something valid."

Okay, somebody asked, does that mean we should apply this patch, or not? After HP's Jeff Vance said sure, install it sooner than later, Tom Emerson offered this advice:

If for some obscure reason this change gets recalled prior to the first change in 2007, then you could actually “roll back” to the prior version because the “new” version would never have taken effect.

I would say if you really wanted to hedge your bets, you could hold off on updating until the day before the next actual DST change in 2007 — provided, of course, you don’t have any software that attempts to calculate (and make use of) “future” dates (and times) that might be past that point. If, as I said, this gets recalled, then you’re good and you don’t have to actually install it after all.

However, once the first change really does take place, if any further changes occur (such as if it gets repealed), then a new file would be necessary because, for a brief period of time, this did take effect, and any software that “looks back in history” would need to take this into account when calculating dates and times “in the past."

And Gilles Schipper, who will be appearing at next weekend's HP 3000 conference on the Gulf Coast outside Houston, added this all-purpose instruction about the changing times of the 3000:

Don’t forget to also modify your SETCLOCK criteria when traversing to and from DST according to the new DST rules to come into effect next year.

For most applications, correct setting of the TIMEZONE at the appropriate date is arguably more important than a correct TZTAB file - although correct instances of both are best.

I’ve taken the liberty to include a sample job stream file from Dave Powell - from the HP 3000 newsgroup of Aug. 8, 2005 — that is suitable for the DST algorithm. (We point to our article on the NewsWire blog from that week for a little background.)

I leave it to the reader to simplify this job stream to eliminate checking the year, since this check is now superflous. The example is suitable for the Pacific timezone.
Adjust accordingly for your own timezone.