You can use the following as a guide to finding the local timezone for various systems depending on the distribution and release. If you change the timezone on a machine, you will at the least want to restart the cron daemon, whatever it is called on your machine, to pick up the change. You would generally be advised to reboot the system, so that all processes which are sensitive to the current time reflect the new timezone.

Windows

systeminfo | findstr /L Zone:

Linux

Ubuntu 14.04.3:
    cat /etc/timezone
Ubuntu 16.04:
    cat /etc/timezone
    ls -l /etc/localtime | sed -e 's:.*zoneinfo/::'
Ubuntu 18.04.4:
    cat /etc/timezone
    ls -l /etc/localtime | sed -e 's:.*zoneinfo/::'
RHEL 5:
    sed -n -e '/ZONE/s:.*"\(.*\)":\1:p' /etc/sysconfig/clock
CentOS 6, RHEL 6:
    sed -E 's:.*"(.*)":\1:' /etc/sysconfig/clock
    sed -n -E '/ZONE/s:.*"(.*)":\1:p' /etc/sysconfig/clock
CentOS 7:
    ls -l /etc/localtime | sed -e 's:.*zoneinfo/::'
CentOS 8:
    ls -l /etc/localtime | sed -e 's:.*zoneinfo/::'
SLES 11:
    sed -n -e '/^TIMEZONE/s:.*"\(.*\)":\1:p' /etc/sysconfig/clock
    sed -n -e '/DEFAULT_TIMEZONE/s:.*"\(.*\)":\1:p' /etc/sysconfig/clock
SLES 15:
    ls -l /etc/localtime | sed -e 's:.*zoneinfo/::'
    sed -n -e '/DEFAULT_TIMEZONE/s:.*"\(.*\)":\1:p' /etc/sysconfig/clock

Also with respect to keeping clocks synchronized over the long term, Linux used to use the ntpd daemon (Network Time Protocol daemon) to keep the clock synchronized with Internet sources. Recent Linux releases have switched to using chronyd for the same purpose. One or the other should be in play. There may be additional setup required in a virtual-machine environment.

Solaris

Solaris 10:
    sed -n -e 's/TZ=\(['"'"'"]*\)\(.*\)\1/\2/p' /etc/TIMEZONE

Solaris 11.3:
    ls -l /etc/localtime | sed -e 's:.*zoneinfo/::'

The Linux and Solaris commands above will yield strings like the following:

America/New_York
America/Los_Angeles
US/Eastern

AIX

  • The value exposed with this command has a complicated form; see man environment for details.
  • The timezone is generally not changed by direct editing of the /etc/environment file.  On AIX 5.3 and lower, use smit chtz for that. On AIX 6.1 and 7.1, use smit chtz_user.
AIX 5.3:
    sed -n -e 's/TZ=\(.*\)/\1/p' /etc/environment