An addition to the job stream Frank posted; setting the TZ variable is also
increasingly important. On our systems, our system-wide UDC XEQ's tz.pub.sys
which is a command file containing simply;

setvar tz "EST5EST"

So I added to Frank's job an ECHO command that overwrites the tz.pub.sys
file with the appropriate timezone. The end of the timezone job on our
system now reads:

!if hpday = 1 and hpmonth = 10 and hpdate > 24 then
!  SETCLOCK TIMEZONE = W5:00
!  ECHO SETVAR TZ "EST5EST" > TZ.PUB.SYS
!  TELLOP *********************************************
!  TELLOP Changing the system clock to STANDARD TIME.
!  TELLOP The clock will S L O W   D O W N until
!  TELLOP we have fallen back one hour.
!  TELLOP *********************************************
!elseif hpday = 1 and hpmonth = 4 and hpdate < 8 then
!  SETCLOCK TIMEZONE = W4:00
!  ECHO SETVAR TZ "EST4EDT" > TZ.PUB.SYS
!  TELLOP *********************************************
!  TELLOP Changing the system clock to DAYLIGHT TIME.
!  TELLOP The clock jumped ahead one hour.
!  TELLOP *********************************************
!endif

So now, our clocks will be set correctly, and so will our TZ vars. :-)

             -Chris Bartram