This is just a reminder to myself. Set the time and date in the BIOS before you install XenServer, or anything for that matter..
Just today, after installing XenServer, I decided to set the date and time in the BIOS before heading out to lunch. The date set in the BIOS was 5/31/2010 so naturally my XenServer 30 day license expired as soon as I adjusted the date. Upon booting, the VMs wouldn’t start because the license had expired as shown below: