If you cannot find /etc/sysconfig/clock , this is probably the case if you are on a disto that does not use it. At least for Ubuntu 15-17 and RHEL / CentOS 7 you can use the timedatectl utility.
Show current settings
timedatectl
List of available time zones
timedatectl list-timezones
Set time zone
sudo timedatectl set-timezone <timezone>
This will take care of changing the symbolic link /etc/localtime .
Links: RHEL Guide , Ubuntu timedatectl (1)
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