Android CDD

As of the 1st September 2017 Android published their updated Compatibility Definitions Document version 8.

9.8.1 . Usage History - Android stores the history of the user's choices and manages such history by UsageStatsManager . Device implementations: [C-1 -1 ] MUST keep a reasonable retention period of such user history. [SR] Are STRONGLY RECOMMENDED to keep the 1 4 days retention period as configured by default in the AOSP implementation.

See also: 9.9. Data Storage Encryption, 9.9.2. File Based Encryption, 9.9.3. Full Disk Encryption,
https://source.android.com/compatibility/android-cdd.pdf