ObjectCache should use phone uptime instead of time

[andrew-ld]

Currently ObjectCache depends on the system time never changing, which is not optimal in a setup where the app runs for a long time, the user or the system might change the time.

a solution would be not to use the time but the uptime of the phone.

https://developer.android.com/reference/android/os/SystemClock#uptimeMillis()

[greenrobot-team]

That API is only available on Android. I guess that's why System time was chosen.

Might make more sense to switch to the new Java 8 Time APIs and allow to supply a custom clock.

[andrew-ld]

agree