convdate: 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/lib/news/bin/convdate - from package: inn2
/usr/lib/news/bin/convdate - from package: inn

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

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