[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: time zone and UTC issue

On 28/11/12 03:26 PM, Andrei POPESCU wrote:
On Mi, 28 nov 12, 14:09:42, Ralf Mardorf wrote:
The Linux has to know if the hwclock does use UTC or not and then it
will set up the clock, when running a Linux to the correct time for your
timezone. IOW you only have to inform what time hwclock does use.

I'm living in Germany, if my hwclock would use UTC time, then saving
e.g. BIOS settings, would add a wrong time to the files. So I can't see
an advantage in using UTC. I'm using local time for the hwclock.
Probably not a major problem, but assuming the computer is physically
moved to a different location you have to change both the BIOS clock and
the timezone configuration, whereas if the hardware clock is set to UTC
you only have to change the timezone configuration.

I can't think of any other issue (assuming correct configuration).

Kind regards,
I note that BIOS clocks don't store or even recognize the time zone. Linux takes the time from the BIOS clock then interprets it using the machine's clock and timezone settings. When the computer is shut down, Linux updates the BIOS clock. In between, it ignores it.

If you have a lap top and fly from one time zone to another, you can set your computer to display local times by changing the time zone setting. This will update the display of times but won't impact how they are stored, which is always in unix time. If you shut down your laptop, it's BIOS clock will be updated with the new local time.

When you restart the laptop, it will use the current BIOS time as a starting point. This can be changed by chrony or ntp, if you are running them.

In short, there is little advantage to using one clock setting over the other. UTC is generally more logical and standard but Windows uses local time (figures), so dual booting will give you headaches (just try running a live CD on a Windows computer - the times will be messed up.

Linux respects and correctly handles whichever time setting you use but unless you are running Windows, there is no reason not to use UTC.

Reply to: