How to change the system time zone
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How to change the system time zone



It may be necesary to change a HP-UX system timezone. Normally, this occured when system are rellocated to new geographical regions. There are to ways to change the system time zone.

The available timezone are define on "/usr/lib/tztab" file. The format of the entries is the following.

0   3   1-7     4     1987-2038        0      UCT5
|   |    |      |         |            |       |> time zone description
|   |    |      |         |            |> day of week (0-6, 0=Sunday)
|   |    |      |         |> year (range)
|   |    |      |> month of year
|   |    |> day of month (range)
|   |> hour
|> minute

Using "set_parms timezone" command

# set_parms timezone

The following procedure enables you to set the time zone.
Select your location from the following list:

  1) North America or Hawaii

  2) Central America

  3) South America

  4) Europe

  5) Africa

  6) Asia

  7) Australia, New Zealand

  8) Russia / CIS

Enter the number for your location (1-7) then press [Enter] 2


You have selected the time zone for all of Central America.

Is this correct?

Press [y] for yes or [n] for no, then press [Enter] y

Your changes will not take effect until you reboot the system.


Do you want to reboot now?

Press [y] for yes or [n] for no, then press [Enter] y

Editing timezone files

To change the system timezone, is necesary to change the contents of two files: /etc/default/tz and /etc/TIMEZONE. The timezone must match between in both files.

The "/etc/TIMEZONE" file is used by daemons that don't have TZ shell variable exported into their environment when they are started. The "/etc/default/tz" is used by processes that relay on the TZ shell variable to keep time tracking.


# cat /etc/default/tz

# cat /etc/TIMEZONE
# @(#)B.11.31_LR
export TZ


  • While it is not strictly required to reboot the system after modifying the rules in the /usr/lib/tztab file, running processes using a timezone with a changed rule need to be restarted to apply the new rules.
  • Processes like cron(1M), which depend on proper interpretation of timestamps in the future, must be restarted as soon as possible.
  • Processes that only timestamp messages, should be restarted before the changes take effect.
  • While it's teoretical possible to establish every individual processes that needs to be restartated, is good policy not to trust that every last one was discovered. The effects of missing a process restart could produce incorrect time stamps or time calculations in the data and applications. Is much better to schedule a maintenance window to reboot the system after changing the system timezone.


Tunable Kernel Parameters

HP-UX Reference Release 11.0 System Calls and File Formats
On page 795 tztab file is explained.

DST Changes for HP High Availability Products


This page was last modified on 19 April 2011, at 19:30. This page has been accessed 3,404 times.