I'm developing an app that is connected to a local network, but without internet. I'm using an APC 8750 card http://apc.io/products/8750a without battery, that is, when it turns off, it loses the calendar. By what means does Android automatically update the calendar? If in the case Android uses a date and time server or NTP on the internet, how to change the server to a servlet on a server in this same local network for example?
In Android's default settings, it uses the time and zone of the cellular network and to change the date and time of the device you will need it to be rooted, as there is no application-level permission to access this cellular feature.