Operating System - OpenVMS

TIMEZONE changed after pass the end of year

waikamon charoenthai
Occasional Advisor

TIMEZONE changed after pass the end of year

My customer use OpenVMS/Alpha V7.3-2 on ES47. And they defined logical name as below:


They use timezone rule is EST-7, (required by their application)
After pass the end of year (from 2007 to 2008). The time zone rule was changed automaticly to GMT-7.
The logical became as below:

It has some problems with their applications. They have to change timezobe by manually.
This event has been happended at the end of year 2006 (From 2006 to 2007). But last time this system was not production so they didn't inform me.
How does the TIMEZONE change? and how to fix it?

Steven Schweda
Honored Contributor

Re: TIMEZONE changed after pass the end of year

> How does the TIMEZONE change?

define /system SYS$LOCALTIME xxx
define /system SYS$TIMEZONE_RULE xxx

It/they could be almost anywhere.

be inconsistent here. Perhaps it would be
in the hope of straighteng things out, and
then try to find any (rogue) command
procedures which mention these logical names.

You could lose the irrelevant TCPIP logical
this way:

show logical SYS$*TIME*
Volker Halle
Honored Contributor

Re: TIMEZONE changed after pass the end of year


the timezone values are being automatically re-defined on 1-JAN through the TQE (Timer Queue Element) invoking JOB_CONTROL to calculate the correct DST change event times for the new year.

The SYS$TIME* logicals should not be manually changed, except by using @SYS$MANAGER:UTC$TIME_SETUP.

Honored Contributor

Re: TIMEZONE changed after pass the end of year

In the POSIX interpretation, GMT+7 is seven hours west of and thus seven hours behind the prime meridian. UTC-7 is the equivalent time zone. In non-POSIX, GMT+7 is seven hours east of and seven hours ahead of the prime meridian. UTC+7 is the equivalent timezone.

The OpenVMS FAQ points to how to set the timezone correctly using the SYS$MANAGER:UTC$TIME_SETUP.COM tool.


I'd suggest not directly accessing, looking at or even considering the logical names, as they are obscure and easy to derail, and failures and errors are subtle and difficult to detect.

The FAQ has some other related materials, and I have a large collection of timezone information for OpenVMS posted at the web site.

Here's the GMT offset description:

GMT+7 is US Mountain time, IIRC. Or GMT+7 under the old and non-POSIX interpretation is Southeast Asia. It all depends on which rules you're using, and the current Olsen timezone rules use the POSIX interpretation. The older Olsen rules didn't.

The whole of the timekeeping discussions are indexed here:

And I'd recommend you avoid using GMT due to the obvious confusion; due to having to distinguish old and new TZ rules. Use of UTC or of a specific zone is a better choice. And use the SYS$MANAGER:UTC$TIME_SETUP.COM tool.

To fix this, you can probably invoke the tool directly and not have to reboot. Pick the appropriate timezone. (Though depending on what logical names got defined and how when the attempt to fix this was made, that a pass of this tool will resolve this not a complete certainty.)

Stephen Hoffman
HoffmanLabs LLC
waikamon charoenthai
Occasional Advisor

Re: TIMEZONE changed after pass the end of year

Thanks for your information. I will test it at testing machine and will inform the result later.

Waikamon C.