From nobody@FreeBSD.ORG  Sat Nov 18 23:20:05 2000
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Date: Sat, 18 Nov 2000 23:20:05 -0800 (PST)
From: seraf@2600.com
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Subject: cron isn't daylight savings-aware
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>Number:         22954
>Category:       bin
>Synopsis:       cron isn't daylight savings-aware
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Nov 18 23:30:01 PST 2000
>Closed-Date:    Sun Nov 19 10:04:52 PST 2000
>Last-Modified:  Sun Nov 19 10:07:37 PST 2000
>Originator:     Dominick LaTrappe
>Release:        4.1-20001102-STABLE
>Organization:
>Environment:
FreeBSD rocketmorton 4.1-20001102-STABLE FreeBSD 4.1-20001102-STABLE #6: Fri Nov 16 01:42:08 UTC 2000     dominick@rocketmorton:/usr/src/sys/compile/MORTON  i386
>Description:
cron(8) doesn't seem to be aware of time zones like PST8PDT which occasionally shift forward or backward by an hour for American "Daylight Savings."  The result is cron jobs being skipped over, or running twice.  This is a really old problem, IIRC.
>How-To-Repeat:
Schedule a cron job which runs within the hour following the pre-shift time of the 1hr-forward-shift (it will never run), or one which runs without the hour preceding the post-shift time of the 1hr-back-shift (it will run twice).  I *think* I have this right.  It's confusing, isn't it?!
>Fix:
Interim solution: Run the affected system in UTC time, or another time zone with an absolute relationship to UTC.
Permanent solution: Make cron use UTC time, or munge cron's understanding of time, or petition the US government to abolish Daylight Savings!

>Release-Note:
>Audit-Trail:
State-Changed-From-To: open->closed 
State-Changed-By: dougb 
State-Changed-When: Sun Nov 19 10:04:52 PST 2000 
State-Changed-Why:  

The problems are actually much more complex than you describe. 
Ultimately, the advice in crontab(5) should be heeded, namely 
don't schedule jobs during that time period.  

http://www.freebsd.org/cgi/query-pr.cgi?pr=22954 
>Unformatted:
