timedatectl: command not found

Have You tried accessing the binary with the full path?

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 Debian possible default full paths are:

/usr/bin/timedatectl - from package: systemd

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