ANDROID_EPOCH_TIME
What it is
Current date and time, encoded as Epoch time (in milliseconds). This value denotes the number of milliseconds seconds that have elapsed since 1/1/1970 UTC.
CarServices will write to this value to give VHAL the Android system's time, if the VHAL supports this property. This can be useful to synchronize other vehicle systems (dash clock etc) with Android's time.
AAOS writes to this property once during boot, and will thereafter write only when some time-source changes are propagated. AAOS will fill in VehiclePropValue.timestamp correctly. Note that AAOS will not send updates for natural elapse of time. int64Values[0] = provided Unix time (in milliseconds)
Note that the property may take >0 ms to get propagated through the stack and, having a timestamped property helps reduce any time drift. So, for all writes to the property, the timestamp can be used to negate this drift: drift = elapsedTime - PropValue.timestamp effectiveTime = PropValue.value.int64Values[0] + drift
How the ID is built
A property ID is a 32-bit value packing four fields. Reading 0x11500606 apart:
| Field | Mask | Value | Means |
|---|---|---|---|
| Group | 0xf0000000 | 0x10000000 | SYSTEM |
| Area | 0x0f000000 | 0x01000000 | GLOBAL |
| Type | 0x00ff0000 | 0x00500000 | INT64 |
| Ordinal | 0x0000ffff | 0x00000606 | 0x606 |
Reading it from an app
This property is defined in the HAL but is not exposed as a constant in android.car.VehiclePropertyIds, so it is not reachable through CarPropertyManager from an ordinary app. It is used by the platform, or by vendor code running with system privileges.