change_tz: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/change_tz - from package: python-vobject

You may install the required package with command yum install {package}

Error in other languages:
change_tz: bevel nie gevind nie
change_tz: comandă negăsită
change_tz: comando não encontrado
change_tz: commande introuvable
change_tz: command not found
change_tz: käsku ei ole
change_tz: không tìm thấy lệnh
change_tz: komanda nerasta
change_tz: Kommando nicht gefunden.
change_tz: kommandot finns inte
change_tz: komut yok
change_tz: nie znaleziono polecenia
change_tz: níor aimsíodh an t-ordú
change_tz: no se encontró la orden
change_tz: no s'ha trobat l'ordre
change_tz: opdracht niet gevonden
change_tz: parancs nem található
change_tz: perintah tidak ditemukan
change_tz: príkaz nenájdený
change_tz: příkaz nenalezen
change_tz: команда не найдена
change_tz: командата не е открита
change_tz: 命令找不到
change_tz: コマンドが見つかりません