Daylight Savings Time

Clyde E. Kunkel clydekunkel7734 at
Wed Nov 4 13:47:32 UTC 2009

On 11/03/2009 08:28 PM, Matthew Saltzman wrote:
> On Tue, 2009-11-03 at 15:32 -0500, Clyde E. Kunkel wrote:
>> On 11/03/2009 11:02 AM, Clyde E. Kunkel wrote:
>>> Should rawhide have set US East Coast Daylight Saving Time back one hour
>>> on Nov 1 to Standard Time?
>> OK, I see I am I wonder why?  The bios on this machine
>> DOES NOT use UTC and the UTC box was unchecked during installation. Does
>> that make a difference?
> Yes.  If you use UTC for the hardware clock, then the right thing is
> always done with regard to DST.
> If you use localtime, then Linux assumes that the hardware clock
> contains the correct local time at boot.  The DST adjustment will take
> place if the machine is running at the time of the transition, and the
> correct time will be saved if the machine is rebooted after that.  If
> the machine is off at the time of the transition and you don't set the
> hardware clock, the time will be an hour off at boot.
>> I also see that since setting the time correctly about 5 hours ago, time
>> has gained 5 minutes.  I recall msgs sometime ago on this list about the
>> clock gaining time in rawhide, so all I may have been seeing was time
>> creep and not an erroneous EDST ->  EST.
> If the machine is connected to the Internet, you should consider using
> NTP to keep your clock in line.

You are correct!  The machine was off during the transition.  That 
explains it.  Also, I used to use NTP, but transistion to the desktop 
took so long I abandoned it.  "Time" to try again.

Thanks for the explanation.  Very useful.

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