How do I permanently reset the time zone in Debian?

Question

Dreamhost seems to think that we like PDT, despite being in the Midwest. How do I change the timezone?

Answer 1

A tool I found to be easier to use is dpkg-reconfigure. Use:

sudo dpkg-reconfigure tzdata

You will be given a multitude of choices, including some that are not included in tzselect.

Answer 2

This is presumably a bit late for the OP, and more intended for other searchers who arrive here.

If you need a non-interactive solution, try this solution from changing timezone with dpkg-reconfigure tzdata and debconf-set-selections

echo "Europe/Zurich" > /etc/timezone 
dpkg-reconfigure -f noninteractive tzdata

You can figure out your timezone by poking around in /usr/share/zoneinfo. In fact the dpkg-reconfigure command above copies the appropriate file from there to /etc/localtime. I used to just do that manually, and it seems to work fine.

Don't be too surprised if long running processes don't pick up the change. eg Apache log timestamps come to mind. Consider whether that matters, and hence whether you need to restart running processes or even reboot.

Answer 3

To edit it non interactively on recent Debian and Ubuntu versions (Stretch/Xenial etc.), you need to remove /etc/localtime as well, otherwise /etc/timezone will be overwritten.

echo 'Europe/Zurich' > /etc/timezone 
rm /etc/localtime
dpkg-reconfigure -f noninteractive tzdata

This answer is based on mc0e' answer. I can not add a comment with my reputation.

Answer 4

TL;DR

echo "TZ=Etc/UTC" >> /etc/environment
tzconfig

where Etc/UTC is your preferred timezone you found using tzselect.

Longer version

When you're using

dpkg-reconfigure tzdata

the timezone information is not kept after reboot. You can verify your settings with

diff -s /etc/localtime /usr/share/zoneinfo/`cat /etc/timezone`

If you're only updating /etc/timezone, the update won't be consistent with /etc/localtime, thus it's better to execute

tzconfig

Use tzselect to find out which time zones actually exists (or simply browse /usr/share/zoneinfo directory).

In POSIX systems the TZ should take precedence before /etc/localtime:

export TZ='Europe/Berlin'
$ date
Tue Apr 10 08:51:03 CEST 2018
export TZ='Pacific/Efate'
$ date
Tue Apr 10 18:28:33 +11 2018

Using directly TZ can save you many system calls as frequently used date/time related functions has to access filesystem each time some program asks for current date. It's a micro-optimization, but quite simple one.