hcal: 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 Debian possible default full paths are:

/usr/bin/hcal - from package: hdate

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

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