ical: 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/ical - from package: itools

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

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