This is not a question. Just some problem I solved and thought I could share it here if someone has the same problem. I considered posting this on General > success stories but on second thought it did not seem like that much of a success and the problem might be Slackware specific. Feel free to move this if it doesn't fit here. But there's still a mystery to be solved. See the bottom of the post.
I am running Slackware 13.37. Since I installed Slackware on this computer in 2007 I have never formatted or reinstalled the OS. I just upgraded as described (might be related).
I recently moved several timezones away from my hometown so I wanted to change the timezone setting.
Changing the timezone looked fairly easy according to a simple web search.
sudo rm -f /etc/localtime
Make a symlink to your new timezone
sudo ln -s /usr/share/zoneinfo/<your_continent>/<your_zone> /etc/localtime
(some sources used ln -sf)
Check if you were able to change the timezone with "date".
Set the time with "date"
(Omitting this because I cannot look up the string format again)
If your hardware clock is set to local time write this new local time to hardware clock
sudo /sbin/hwclock --systohc
My problem: the symlinking step did not appear to work. After creating the symlink and checking the timezone with "date", I saw that the timezone remained the same as that of my hometown. Instead of sudoing I tried again as root to no avail.
My solution: Out of desperation I looked at the content of timezone files in /usr/share/zoneinfo. They are mostly gibberish, but in the last line you can make out the timezone abbreviations. I checked several files and saw that the timezone abbreviations were the same as that of my hometown timezone. Weird.
So I decided to reinstall glibc-zoneinfo which has the timezone lists and information.
sudo /usr/sbin/slackpkg reinstall glibc-zoneinfo
When slackpkg prompted I chose the "overwrite" option.
After this, the steps I described above worked smoothly. My timezone is correct, time is correct.
Mystery: Out of curiosity I looked at the contents of the new timezone files in /usr/share/zoneinfo. They all had the correct timezone abbreviations in their last lines. What struck me was that these files were much shorter than my original timezone files. I don't know how I messed them up, how they ended up much longer then they were supposed to be.