By NTP you mean Network Time Protocal?
By design CallPilot and Symposium servers get their time from the PBX. I am not aware of a way to get the PBX to sync time with a NTP server.
I understand that the best that can be none is to setup a PC that gets it's time from a NTP server to run a script, procomm for example, to update the time on the PBX say once a day to match the NTP time.
Might be some better ways to do this but I just have not figured one out yet.