On the Network Time Protocol Configuration page in EM:
You will need to know:
1. the IP address of your preferred NTP (network time protocol) server, and optionally a secondary NTP server.
2. If your NTP servers run in Secure or Insecure mode. If they are secure, then you will need to know the key id and Private Key for your servers.
If you can ping your NTP server(s) from the Call Server, then select 'Directly from Call Server' in the Communication Path field.
If you cannot ping your NTP server(s) from the Call Server, but you can from your Signaling Server, then select 'Through Signaling Server' in the Communication Path field.
Fill out the information for the Primary Server - IP address, Transfer mode, and if necessary credentials. Do the same for the Secondary Server if you have one.
Check Automatic Background Time Synchronization.
Select an interval to automatically sync the PBX time with your network time. The Query offset allows you to set the minutes past the hour when the time will sync.
Choose your time zone.
Depending on your patch level, you may or may not need to check the Daylight Saving Time box. If your time is wrong after you sync, then come back in and change the setting. Just remember that it may take several minutes for the time on your phone to update, as the phone sets do not set their clock in real time with the pbx.
Click Save to return to the System Date and Time page in EM, then click the Sync Now button. The PBX time should now be synced with your network.