Bug 1986 - cron skips jobs on first day of DST
cron skips jobs on first day of DST
Product: Red Hat Linux
Classification: Retired
Component: vixie-cron (Show other bugs)
All Linux
low Severity low
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Assigned To: Crutcher Dunnavant
Depends On:
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Reported: 1999-04-04 16:04 EDT by hargrove
Modified: 2008-05-01 11:37 EDT (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2001-04-10 18:01:46 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description hargrove 1999-04-04 16:04:17 EDT
Because the clock doesn't pass through the times 2:00-2:59
on the first day of daylight savings time, jobs (such as my
daily backups!) that are scheduled to begin anytime in this
one hour window are skipped.

Arguably this is correct in the sense that these times don't
exist, but if this behavior is to be considerd "normal",
then the man page should warn users about this.
Comment 1 David Lawrence 1999-04-06 15:53:59 EDT
Your suggestion has been passed on to a developer for further review.
Comment 2 Michael K. Johnson 1999-04-14 13:17:59 EDT
I have reviewed the Single Unix Specification definition of crontab
(it doesn't talk about cron specifically, but the crontab definition
talks about the crontab format as well) and there is no indication
that cron should magically re-schedule jobs that are scheduled for a
non-existant time.  Indeed, it is not clear what the right thing to
do would be if cron tried to shuffle the schedules.

I have reclassified this bug report as a documentation bug report
and we'll change the man page to explicitly mention that cron will
not run jobs during times that do not exist, such as during daylight
savings time conversions.
Comment 3 Michael K. Johnson 1999-04-14 13:40:59 EDT
Man page updated with this information in vixie-cron-3.0.1-32
Comment 4 Jeremy Sanders 2002-11-22 07:41:41 EST
Following up on this, in RedHat 7.3, the cron manpage makes no mention of
daylight saving time. It is not clear whether some jobs may be run twice or not
at all.

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