today: 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/today - from package: mhc-utils

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

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