xcalpr: 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/xcalpr - from package: xcal

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

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