The /etc/localtime file configures the system-wide timezone of the local system that is used by applications for presentation to the user. It should be an absolute or relative symbolic link pointing to /usr/share/zoneinfo/, followed by a timezone identifier such as "Europe/Berlin" or "Etc/UTC". The resulting link should lead to the corresponding binary tzfile(5) timezone data for the configured timezone.
Because the timezone identifier is extracted from the symlink target name of /etc/localtime, this file may not be a normal file or hardlink.
The timezone may be overridden for individual programs by using the TZ environment variable. See environ(7).
You may use timedatectl(1) to change the settings of this file from the command line.