sync - What is the synchronization source for the internal clock

Using a tool to compare the internal clock of my Android device to internet time servers, I noticed my device is 30 seconds wrong.

So that made me wondering what is the cause of this error. Where does Android gets it time from, so I can adjust or complain there:

I can think of the following sources:

• Provided by the cellular network provider.



• From GPS.


• From a NTP server on the local WIFI network.


• A global NTP server (hosted by Google)?