Question about DST changes in the US

[Matthew Saltzman]

On Wed, 14 Feb 2007, Michael Klinosky wrote:

> Ian:
>> Just off the cuff: If your system is set to use UTC, local time and changes 
>> will be applied when Fedora boots.
>
> NTP-aware systems shouldn't have any problem - correct? (I figure that the 
> time servers will change on the new days.)
>
> I checked ntp.org and the timeservers site - didn't mention anything about 
> the new dates.

If the Linux system is running at the time of the change, it will do the 
Right Thing whether set to local or UTC, whether ntp or not.

If the Linux system is not running at the time of the change, it will do 
the Right Thing if it is UTC.  If it is local, it will always assume the 
hwclock has the correct local time on boot.

If you dual-boot Windows, what happens depends on which system is running 
at the change time and which system is booted next and whether you use UTC 
(which requires living with GMT as your Windows time zone) or local time 
(which requires paying attention).

I'm not sure about NTP systems, but there is some delay between the 
setting of the system clock from the hwclock at startup and the startup of 
ntpd.  So there may be a short (or longer if you use NetworkManager) delay 
between startup and clock correction.

-- 
 		Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs