Daylight saving time changes in MIT kerberos?

Jeffrey Hutzelman jhutz at
Fri Oct 13 15:15:05 EDT 2006

On Friday, October 13, 2006 09:54:19 AM -0400 Danny Mayer 
<mayer at> wrote:

> What are you talking about? Timezones are local display issues. When you
> go from summer time to winter time and visa versa do you see issues? All
>  applications use UTC which doesn't care about timezones.

Unfortunately, this is not entirely true.  Certain operating systems track 
local time, rather than UTC, and thus will report incorrect UTC times to 
applications if the timezone is not correct.  Further, users are prone to 
deciding that the time they see is wrong and "fixing" it by changing the 
time rather than selecting the correct timezone.  It seems not unlikely 
that a good portion of users will do so in response to the upcoming 
brokenness ("Oh, I know the rules changed; my computer must have done it 
wrong, so I'll just set the clock now").

Of course, systems using NTP with a reliable time source should have no 
problems, as long as the user does not tamper with the clock.

-- Jeffrey T. Hutzelman (N3NHS) <jhutz+ at>
   Sr. Research Systems Programmer
   School of Computer Science - Research Computing Facility
   Carnegie Mellon University - Pittsburgh, PA

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