Acucorp joins midrange alliance
Understanding how SLTs work

All in a Day(light Saving Time)'s Work

Four weeks from this Sunday we will see the first change in many years to the "spring-forward" date for Daylight Saving Time, and the HP 3000 community has already started to discuss how they plan to handle it.

HP has released a revised TZ table for MPE/iX, an important part of keeping 3000s on the correct time during the roll-forward of one hour at 2 AM Sunday, March 11. That date will be advanced by three weeks from the one US customers have used since 1987. In 1974, the US daylight saving time began on January 6, and in 1975 it began on February 23.  After those two nascent years for the 3000, the DST starting date from 1976 onward was the last Sunday in April. A 1986 law shifted the starting date to the first Sunday in April, beginning in 1987.

We would guess that 20 years of the same DST dates — the late October change-back date has always been in place, up to this fall — covers the experience of four out of every five HP 3000 managers. (If you remember the first 1974 DST and were running a 3000, we'd love to hear your story. Even if you were running a 3000 in '76, you've got a good story.)

So this is a big change for some managers of 3000s. A recent discussion on the 3000 newsgroup included help from consultants, pointers at the HP files and notes about HP-UX and Windows accomodations. It looks like it won't be something to spend a lot of time on, so long as your tables are up to date.

Gilles Schipper, our Homesteading Editor, offered this advice, in addition to using an updated TZTAB file, during an earlier discussion of the change:

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.

Schipper took note of Dave Powell's jobstream to check and adjust for the new DST time (Powell's example being for the Pacific US time zone):

!#   Check for Daylight Saving Time change -- NEW  (readable?)
!IF  HPDAY = 1
!    IF  HPYYYY <= 2006
!        IF  HPMONTH = 4   AND   HPDATE < 8
!            SETCLOCK TIMEZONE = W7:00
!        ELSEIF  HPMONTH = 10   AND   HPDATE > 24
!            SETCLOCK TIMEZONE = W8:00
!        ENDIF
!    ELSE
!        IF  HPMONTH = 3   AND   HPDATE >= 8   AND   HPDATE <= 14
!            SETCLOCK TIMEZONE = W7:00
!        ELSEIF  HPMONTH = 11   AND   HPDATE <= 7
!            SETCLOCK TIMEZONE = W8:00
!        ENDIF
!    ENDIF

The new TZTAB file and a jobstream are also available at Beechglen's Web site. Beechglen's article notes that you want to change that TZTAB file during a quiet time for your system, since "programs are constantly accessing the file. While the installation is a simple rename or copy, it is still advisable to install it with exclusive access to the system or during a period of low activity." Beechglen also has an ASCII version of the new TZTAB file, if store-to-disk delivery is "cumbersome," as the article says.

John Bawden, who managed the Qualchoice HP 3000 operations for many years, is also offering to help 3000 managers through the change at his consulting company, Homestead3000 Consulting.

After that, of course, the 3000 newsgroup chatter drifted to why the DST was instituted, which devices might already know about the change coming up, and where you can get good flourescent light bulbs — which the 3000 community was pretty sure saves more energy than any DST period.