The timezone a server is configured with can be shown with the date command.
$ date +%Z
EDT
To change the timezone in CentOS 6, first ensure you have the latest tzdata package installed.
$ yum install tzdata
Then update the /etc/localtime with the new timezone by copying the timezone file the tzdata package.
$ cp /usr/share/zoneinfo/UTC /etc/localtime
$ date +%Z UTC
