easter: 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 CentOS possible default full paths are:

/usr/bin/easter - from package: perl-Date-Easter

You may install the required package with command yum install {package}

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