Oracle VM Manager uses certificate-based authentication to maintain secure communication with the Oracle VM Agent that runs on each Oracle VM Server instance. This means that the system time on each Oracle VM Server must be within the bounds of the certificate valid from and valid to timestamps, or certificate validity is challenged and Oracle VM Manager is unable to authenticate to the Oracle VM Agent.

In most instances, this is not a problem, since servers are automatically configured to use the Oracle VM Manager as an NTP server as soon as ownership is taken. However, during server discovery the Oracle VM Manager uses a password to perform its initial authentication against a server and to provide its certificate for ongoing communication. During this phase of discovery, a check is performed to ensure that the system time on the Oracle VM Server is within the bounds required for certificate authentication to take place. If this is not the case, discovery fails and an error message is returned:

OVMAPI_4024E: Cannot take ownership of server myserver5.virtlab.info because the date 
and time on the server are outside the valid range for the manager's SSL certificate.  
The certificate is valid from 10/24/13 7:37 PM to 10/25/23 7:37 PM, but server's timestamp 
is 9/28/13 8:14 PM.  Please verify the server's NTP and time settings.

In this situation, it is necessary that you access the affected Oracle VM Server directly and update its system time manually before attempting to rediscover the server using Oracle VM Manager. Once Oracle VM Manager has completed discovery and is able to take ownership of the server, its NTP configuration is updated automatically and it remains synchronized with the Oracle VM Manager host.