topic Re: Daylight savings issue in Operating System - HP-UX

Daylight savings issue

Sebastien Masson — Mon, 18 Mar 2002 19:59:50 GMT

Ok gang, I have a good one for all of you.

I want to know the impact of the Daylight Saving time in the schedule of Omniback or cronjob (omniback schedule is drive by cron anyway).

I'm in the Eastern Time with daylight saving fu.. sh..

I know the two black hole that I job may not run at all if we add one hour and job can be run twice if we reduce an hour.

Please I want your opinion on that.

Re: Daylight savings issue

A. Clay Stephenson — Mon, 18 Mar 2002 20:09:52 GMT

If you simply do a man cron, it explains this very well. The short answer is that you don't need to do anything special.

Re: Daylight savings issue

John Payne_2 — Mon, 18 Mar 2002 20:25:09 GMT

cron is smart enough to take care of things for you. On a "fall-back", it only runs on the first occurance. On the "spring-ahead" it runs at the time that it should have had the time not changed at all. (If it was supposed to run at )1:30, but 01:30 did not happen, then it will run at 02:30 instead, for example.)

John

Re: Daylight savings issue

Darrell Allen — Mon, 18 Mar 2002 20:32:50 GMT

Hi,

Cron jobs will not be skipped in the Spring nor executed twice in the Fall. Cron handles that rather well.

There is a potential timing issue. Consider the following:
JobA is scheduled to run at 2:30 AM.
JobB is scheduled to run at 3:30 AM.
On the morning of the Spring time change, both jobs would actually be run at 3:30 AM. You can see where that could be an issue if JobB expects JobA being completed.

If JobA was scheduled for 2:45 AM, it would actually be executed after JobB (at 3:45 AM).

Just something to be aware of.

As Clay says, man cron. You can search the forums for other threads on this subject but the man page is the best thing to check.

Darrell

Re: Daylight savings issue

harry d brown jr — Mon, 18 Mar 2002 20:46:22 GMT

Sebastien,

But it won't work correctly in Quebec unless the local language is set to fr_FR.iso88591:

export LANG=fr_FR.iso88591

:-)) --> hehehe

live free or die
harry

Re: Daylight savings issue

Ross Martin — Wed, 20 Mar 2002 01:05:49 GMT

If all is well with HPUX, then daylight savings is automatic and cron will not be effected.

Check your system settings for correct time change information.

The time change information on your system are controlled by a file called /usr/lib/tztab.

The file /usr/lib/tztab has entries with time zone information for different areas all around the world. Where daylight saving applies,
the relevant entry will set the day and time when the system should adjust forward or back in accordance with local daylight saving procedures.

The tztab file relies on your system having the correct TZ variable set for
your area. Check your TZ variable with the 'echo' command.