Setting timezones

Joshua Layne joshua at willowisp.net
Mon Nov 12 17:15:33 CET 2007


Robert Withrow wrote:
> Sorry to reply to my own message, but I discovered that /etc/profile
> sets the TZ environment variable if /etc/localtime doesn't exist.  If I
> unset TZ (or log out and in again) the below works.  Maybe I'll put this
> into the Wiki.
>   
That (wiki help) would be great.

Also, there have been a few entries on the wiki (I am one of the guilty 
parties... :P) about auto-setting timezone data.
The basic use case is this:
if I travel, I want my timezone updated, but not the system clock (which 
should be UTC if it is a good little linux system...) - then all 
calendar entries (which should be stored in UTC internally!) would be 
accurate.
There are two sources that could automate this:
1) the local time that is broadcast from the GSM towers - an offset 
could be calculated and an _appropriate_ timezone could be automatically 
chosen (note that there can be more than one timezone with the same 
offset at a given time of the year, so it would not be able to 
distinguish between those, although perhaps there could be a 'favorites' 
list of timezones in the user's profile) - at minimum, the offset would 
be correct.
2) there is a gps and provided an appropriate lookup table, timezone 
could be determined unequivocally - the problem with this method is that 
I don't know of any free source of this data (geocoded), but it may exist.

I honestly think the first is the easiest to implement, and would work 
on _any_ gsm phone, not just one with an embedded GPS, so would be more 
portable.  The second is undoubtedly more accurate.

Is there a good way to interface to tzdata without requiring 
logout/login? force reload in a session?  Does it require separate ipkgs 
for each timezone, or is there a way to just enter the offset? (I would 
argue that when you are traveling, you only care about the offset 
anyway) Is this a dbus interface? a scripting interface? how to make it 
non-hackish?

I would appreciate thoughts on this.  There hasn't been a lot of 
activity on the wiki around it.

Apologies if this is viewed as thread-jacking.  Not intended as such - I 
just feel that with a 'location-aware' device, a user shouldn't have to 
enter things like timezone - the system should just 'know'.

thanks,
joshua
> Robert Withrow wrote:
>   
>> I've searched the Wiki and the mailing lists and the Internet in
>> general, and what I see for setting the timezone on my Neo is to either
>> install "timezones" or "tzdata" and the link the appropriate thing into
>> /etc/localtime.  Neither way works for me.
>>
>> This is with tzdata, but I get the same result using timezones and
>> timezone-america:
>>
>> root at fic-gta01:/usr/share/zoneinfo$ date
>> Thu Nov  1 23:48:10 UTC 2007
>> root at fic-gta01:/usr/share/zoneinfo$ ipkg install tzdata-americas
>> tzdata-posix
>> Installing tzdata-americas (2007e-r0) to root...
>> Downloading
>> http://buildhost.openmoko.org/OM2007.2/tmp/deploy/glibc/ipk/armv4t/tzdata-americas_2007e-r0_armv4t.ipk
>> Installing tzdata-posix (2007e-r0) to root...
>> Downloading
>> http://buildhost.openmoko.org/OM2007.2/tmp/deploy/glibc/ipk/armv4t/tzdata-posix_2007e-r0_armv4t.ipk
>> Configuring tzdata-americas
>> Configuring tzdata-posix
>> root at fic-gta01:/usr/share/zoneinfo$ ln -s
>> /usr/share/zoneinfo/posix/US/Eastern /etc/localtime
>> root at fic-gta01:/usr/share/zoneinfo$ date
>> Thu Nov  1 23:49:19 UTC 2007
>> root at fic-gta01:/usr/share/zoneinfo$ ls -l /etc/localtime
>> lrwxrwxrwx    1 root     root           36 Nov  1 23:49 /etc/localtime
>> -> /usr/share/zoneinfo/posix/US/Eastern
>> root at fic-gta01:/usr/share/zoneinfo$ /bin/date
>> Thu Nov  1 23:50:23 UTC 2007
>>
>> What stupid mistake am I making?
>>
>>   
>>     
>
>   




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