tzdata-update: 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/sbin/tzdata-update - from package: glibc-common

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

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