ADR 0002: Android system time update capability

Question

Can NTP Check update the Android device system time?

Finding

For a normal Play/user-installed Android app: no. Android protects system clock changes behind privileged APIs/permissions. An app can measure offset and show guidance, but it cannot directly set wall-clock time unless it is installed with elevated trust.

Practical options

Normal app behavior for v1
- Probe NTP servers.
- Show estimated device offset.
- Warn when local clock appears wrong.
- Provide a button to open Android Date & Time settings.
- No special permissions beyond INTERNET.
Device-owner / enterprise-managed device
- Some Android management APIs allow a device owner/profile owner to control certain time/timezone policies depending on Android version and ownership mode.
- This requires provisioning the app as a device policy controller, not a typical install.
Privileged/system app or custom ROM
- A system-signed or /system/priv-app application can use privileged permissions such as android.permission.SET_TIME.
- This is not available to ordinary APK installs.
Rooted device helper
- A rooted-device mode could call shell commands such as date/toybox date, but this is out of scope for v1 and has safety/security risks.

Decision

V1 will not set Android system time. It will remain a diagnostic/comparison tool and may include an "Open Date & Time settings" action. Any future clock-setting mode must be explicitly separate and gated as enterprise/device-owner, privileged-system, or rooted-device functionality.

Product implication

Market the app as an NTP testing and comparison dashboard, not as a general Android time synchronization daemon.

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