ntptime: 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/ntptime - from package: ntp

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

On Debian possible default full paths are:

/usr/sbin/ntptime - from package: ntp

You may install the required package with command apt-get install {package}

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