How to set your time zone (Shallow Thoughts)

Akkana's Musings on Open Source, Science, and Nature.

Fri, 16 May 2008

How to set your time zone

My laptop's clock has been drifting. I suspect the clock battery is low (not surprising on a 7-year-old machine). But after an hour of poking and prodding, I've been unable to find a way to expose the circuit board under the keyboard, either from the top (keyboard) side -- though I know how to remove individual keycaps, thanks to a reader who sent me detailed instructions a while back (thanks, Miles!) -- or the bottom. Any expert on Vaio SR laptops know how this works?

Anyway, that means I have to check and reset the time periodically. So this morning I did a time check and found it many hours off. No, wait -- actually it was pretty close; it only looked like it was way off because the system had suddenly decided it was in UTC, not PDT. But how could I change that back?

I checked /etc/timezone -- sure enough, it was set to UTC. So I changed that, copying one from a debian machine -- "US/Pacific", but that didn't do it, even after a reboot.

I spent some time reading man hwclock -- there's a lot of good reading in that manual page, about the relation between the system (kernel) clock and the hardware clock. Did you know that you're not supposed to use the date command to set the system time while the system is running? Me neither -- I do that all the time. Hmm. Anyway, interesting reading, but nothing useful about the system time zone.

It has an extensive SEE ALSO list at the end, so I explored some of those documents. /usr/share/doc/util-linux/README.Debian.hwclock is full of lots of interesting information, well worth reading, but it didn't have the answer. man tzset sounded promising, but there was no such man page (or program) on my system. Just for the heckofit, I tried typing tz[tab] to see if I had any other timezone-related programs installed ... and found tzselect. And there was the answer, added almost as an afterthought at the end of the manual page:

Note that tzselect will not actually change the timezone for you. Use 'dpkg-reconfigure tzdata' to achieve this.
Sure enough, dpkg-reconfigure tzdata let me set the time zone. And it even seems to be remembered through a reboot.

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[ 10:04 May 16, 2008    More linux | permalink to this entry ]