Ok, there is one on the phone and one on the UCM.
The phone needs one as it may not be connected to a PBX all the time and/or to whatever it is connected to does not act as a NTP server and as such it needs the capability to have its own settings.
As the phone is showing something different than that of the UCM, it also means that either you did not provision the phone using Zero-Config or if you did, you did not set the following option in the template -
The above is a template that I created for a 1628. You will note that I have set the IP address of the NTP server to a local IP which happens to be the IP of the UCM. I have also set the timezone for my locale and combined with the below -
I have told the UCM to act as a NTP server and as such the phones will use the UCM and get their time from same so that all are in sync with one another.