In the homeassistant app, the notification timestamp is generated when the push message is received by the app. Delays caused by servers, device load, or network latency/availability will delay those pushes - so in the following case:
1:00 - A dog is detected in the front
1:02 - It stops moving around or leaves view, last notification push sent
1:05 - The phone connects to the network
The user, seeing the alert at 1:05, will see that the notification occurred "a few seconds ago", since the timestamp the app sends to the OS was at 1:05. By adding the `when` parameter, it will instead correctly show that the event was triggered at 1:00.
This is exacerbated by the fact that the default behavior of android pushes won't wake the device from deep sleep - in order to receive it as a high priority notification, the additional parameters
```
data:
priority: high
ttl: 0
```
have to be added.
