shutdown by Cron

My english it not perfect. Please excuse that.
I have install the Proxmox VE 3.1 – 21 on a local PC. I need this Server only from 8am to 22pm. So i search an idea to shutdown the Proxmox automatically.

I stopped the Win7 Vms by an Script. – It runs good.

Then i try to stop the Proxmox via Cron an shutdown-h is nothing happen.

Have you an idea?