[ntp:questions] Kind of OT : GMT timezones in linux

Stelios Koroneos stelios at stelioscellar.com
Wed Jun 27 12:12:29 UTC 2007


Greetings to all !

I am sorry if this OT for the list but it conserns an embedded system
running an ntp client  and we are running out of ideas on a problem we
stambled upon,
during the development of a user interface for an embedded device running
linux

We need to let the user set the timezone (and ntp server/update time)  but
due to memory constrains we need to display only GMT times and then link
locatime to /usr/shared/zoneinfo/Etc/GMTXXX where XXX is the user choice for
a timezone
Running a test we realized that the time reported by the system was wrong
and looking into it we found that if we link localtime to GMT+3 for example
we actually got GMT-3 time reported by the system.
Linking localtime into a city with the same time difference things worked
fine.

i.e (Athens is GMT+2 plus 1 hours for Daylight savings)

amalthia:/etc# ln -s /usr/share/zoneinfo/Europe/Athens localtime
amalthia:/etc# date
Wed Jun 27 14:48:17 EEST 2007
amalthia:/etc# rm localtime
amalthia:/etc# ln -s /usr/share/zoneinfo/Etc/GMT+3 localtime
amalthia:/etc# date
Wed Jun 27 08:48:32 GMT+3 2007
amalthia:/etc# rm localtime
amalthia:/etc# ln -s /usr/share/zoneinfo/Etc/GMT-3 localtime
amalthia:/etc# date
Wed Jun 27 14:48:54 GMT-3 2007

Also i was under the impression that GMT should be between (-12 to +13) and
it looks like the filenames are  "reversed" in the zoneinfo/Etc dir (ie from
GMT-13 to GMT+12)
Any idea why is that happening ? Is it something we are doing wrong or do
not understand ? is it a bug ?
What should be the correct way to set the localtime to a GMT zoneinfo ?

Thanks in advance for your time



Stelios S. Koroneos

Digital OPSiS - Embedded Intelligence
http://www.digital-opsis.com







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